Gut endocrine cells possess the capacity to take up and decarboxylate biogenic amine precursors. Decarboxylation is mediated by aromatic L-amino acid decarboxylase (AADC) which is encoded by mRNAs differing in their 5' untranslated regions (UTR) depending on the usage of alternative first exons, 1a and 1b, each with its own acceptor site (-13 and -8 bases relative to the translation start site, respectively). We describe here a novel splice variant of exon 1a-AADC mRNA in rat antral mucosa. Both exon 1a and 1b mRNAs were expressed in rat antral mucosa, but the 1a form was spliced into the acceptor site usually associated with exon 1b (-8). An enteroendocrine cell line (STC-1) expressed exon 1a or exon 1b mRNAs spliced into the -8 acceptor site of exon 2. Transient transfection of a range of cell lines with reporter constructs revealed that all three 5' UTRs efficiently supported expression of the Luciferase reporter. There is therefore a novel, functional 5' UTR of AADC mRNA in rat antral mucosa; alternative AADC splice variants could provide the capacity for control at the level of mRNA translation.

Stimulation of left ventricular mechanoreceptors was believed not only to exert important effects on the circulation, but also to influence the responses to baroreceptor reflexes. However, most previous work is flawed due to inadequate localisation of stimuli to specific reflexogenic areas. In this study, we applied a discrete stimulus to left ventricular mechanoreceptors to examine other reflexes known to effect the circulation. Dogs were anaesthetised, artificially ventilated and a cardiopulmonary bypass established. The pressure distending the left ventricle was controlled through an apical cannula with the aortic valve obstructed by a balloon. Changes in ventricular systolic and end-diastolic pressure had only a small effect on vascular resistance, assessed as perfusion pressure in the systemic circulation (flow constant). Responses to changes in carotid or coronary pressure or to stimulation of chemosensitive afferents by injecting veratridine into the coronary circulation were always much larger. Responses to stimulation of these reflexes were little affected by the level of stimulus to the ventricular receptors. These experiments confirm that responses to stimulation of ventricular mechanoreceptors are very small and show that they remain small at different levels of input to other baroreceptive regions. There was no evidence of interaction between ventricular mechanoreceptor reflexes and carotid or coronary baroreceptors or ventricular chemosensitive reflexes. Experimental Physiology (2001) 86.3, 381-390.

In this study the effects of changes in extracellular magnesium ([Mg2+]o) and calcium ([Ca2+]o) concentrations on basal and on nerve-mediated and acetylcholine (ACh)-evoked in vitro amylase release and calcium mobilization were investigated in rat parotid gland tissue. In the presence of a normal (2.56 mM) [Ca2+]o, both zero (0 mM) and an elevated (10 mM) [Mg2+]o significantly attenuated basal and ACh-evoked amylase release compared to the response obtained in normal (1.1 mM) [Mg2+]o. During electrical field stimulation (EFS) of parotid tissues, only elevated [Mg2+]o reduced amylase release. In a Ca2+-free medium, both basal and ACh-evoked amylase output were markedly reduced compared to the responses obtained under similar conditions in normal [Ca2+]o. Again, the ACh-induced amylase release in a Ca2+-free solution was larger in normal [Mg2+]o than when the [Mg2+]o was either zero or was elevated to 10 mM. Perturbation of [Mg2+]o had no significant effect on basal intracellular free calcium concentration ([Ca2+]i) in parotid acinar cells loaded with the fluorescent Ca2+ indicator fura-2. Both zero Mg2+ and an elevated [Mg2+]o significantly reduced the ACh-induced rise in the peak and the plateau phase of the Ca2+ transient that was seen in normal [Mg2+]o. In parotid acinar cells loaded with the fluorescent Mg2+ indicator magfura-2, ACh elicited a gradual decrease in intracellular free Mg2+ concentration ([Mg2+]i) to below the basal level. The results indicate that both hypo- and hypermagnesaemia may reduce both basal and ACh-evoked amylase secretion from the salivary gland. As far as the ACh-evoked response is concerned, the effect may be exerted by a decrease in cellular Ca2+ transport. Experimental Physiology (2002) 87.3, 321-326.

The aim of this study was to evaluate myofibrillar creatine kinase (CK) activity and to quantify the substrate channelling of ATP between CK and myosin ATPase under different pH conditions within the integrity of myofibrils. A pure myofibrillar fraction was prepared using differential centrifugation. The homogeneity of the preparation and the purity of the fraction were confirmed microscopically and by enzymatic assays for contaminant enzyme activities. The specific activity of myofibrillar CK reached 584 ± 33 nmol PCr min-1 mg-1 at pH 6.75. Two methods were used to detect CK activity: (1) measurement of direct ATP production, and (2) measurement of PCr consumption. This method of evaluation has been tested in experiments with isolated creatine kinase. No discrepancy in CK activity between the methods was observed in the pH range tested (6.0-7.5). However, the same procedures resulted in a significant discrepancy between the amounts of reacted PCr and produced ATP within the pure myofibrillar fraction. This discrepancy represents the portion of ATP produced by the CK reaction, which is preferentially channelled to the myosin ATPase before diffusing into the bulk solution. The maximum evaluated difference reached 42.3 % at pH 6.95. The substrate channelling between myofibrillar-bound CK and myosin ATPase was evaluated under various pH levels within the physiological range and it reached a maximum value in a slightly acidic environment. These results suggest that ATP/ADP flux control by the CK system is more important at lower pH, corresponding to the physiological state of muscle fatigue. Experimental Physiology (2003) 88.1, 1-6.

We have investigated the effect of temperature upon the rate-dependent decrease in the L-type Ca2+ current (iCa) in isolated rat ventricular myocytes. Increasing the rate of stimulation from 0·5 to 3·0 Hz for 30 s induced a reversible decrease in iCa which was temperature dependent. Compared to control (0·5 Hz), the first beat at 3 Hz was decreased by 38 ± 7 % at 22¡C and by 9 ± 1 % at 37¡C (mean ± S.E.M., n = 5, P < 0·05) and, after 30 s of 3 Hz stimulation, iCa was reduced by a further 26 ± 4 and 21 ± 2 % at 22 and 37¡C, respectively. The magnitude of this secondary decline was not significantly different at the two temperatures (P = 0·29). Corroboratory results were obtained from cell-attached patches which also illustrated that the rate-dependent decrease in iCa resulted from a reduction of open channel probability. Paired pulse experiments showed that the greater initial rate-dependent decrease in iCa at 22¡C occurred as a result of slower recovery from fast inactivation processes at 22 than at 37¡C. Recovery of the channel from fast inactivation was very temperature sensitive with a Q10 of 5·6. In contrast, the secondary, progressive decrease in iCa, which results from incomplete recovery from ultra-slow voltage-dependent inactivation, was similar at the two temperatures and appears to be much less temperature dependent.

Species differences in response to hypoxic damage have been observed in studies using whole hearts. The aims of this study were to determine whether (i) species differences in response to simulated hypoxia could be detected at the level of the single myocyte, and (ii) there were any interspecies differences in the Ca2+ handling properties of the cells. Ventricular myocytes were isolated from hearts of adult rats and guinea-pigs and electrically stimulated on the stage of a fluorescence microscope. Cell length was measured using an edge-tracking device, and total intracellular [Ca2+] ([Ca2+]i) determined using indo-1. Cells were exposed to metabolic inhibition (MI) (2.5 mM NaCN and no glucose) to simulate hypoxia followed by washout of CN and re-addition of glucose ('reperfusion'). Following exposure to MI, rat cells underwent rigor contracture in 18.8 ± 0.8 min (n = 80 cells), whereas the time was longer for guinea-pig cells (32.9 ± 1.2 min, n = 83) (P < 0.001). If cells were reperfused after 1-5 min in rigor, then rat cells showed improved morphological recovery compared with guinea-pig cells (P < 0.05); thereafter recovery decreased with increasing time spent in rigor, and was similar in both groups. In indo-1 loaded cells, [Ca2+]i was significantly increased in cells from both species at the end of MI; however, the actual increase was much higher in guinea-pig cells. Upon reperfusion, [Ca2+]i recovered fully in rat cells, but in guinea-pig cells there was no significant decrease. The restoration of [Ca2+]i to normal levels in rat cells following MI was associated with improved contractile recovery compared with guinea-pig cells. We conclude that rat cells are more resistant to effects of MI than are guinea-pig cells; this may be related to species differences in Ca2+ handling during and following exposure to MI. Experimental Physiology (2000) 85.5, 505-510.

Increasing blood bicarbonate content has long been cited as a potential mechanism to improve contractile function. We investigated whether sodium bicarbonate-induced metabolic alkalosis could positively affect force development during the rest-to-work transition in ischaemic skeletal muscle. Secondly, assuming it could, we investigated whether bicarbonate could augment acetyl group availability through the same equilibrium reaction as sodium acetate pre-treatment and whether this underpins, at least in part, its ergogenic effect. Multiple biopsy samples were obtained from the canine gracilis muscle during 5 min of electrically evoked ischaemic contraction, which enabled the determination of the time course of acetyl group accumulation, substrate utilisation, pyruvate dehydrogenase complex activation and tension development in animals treated with saline (control; n = 6) or sodium bicarbonate (n = 5). Treatment with bicarbonate elevated acetylcarnitine content above the control level at rest (P<0.05), but at no time point during subsequent contraction. The pyruvate dehydrogenase complex was activated following 40 s of contraction in both groups, with no differences existing between treatments at any time point. The requirement for ATP resynthesis from non-oxygen-dependent routes was no different between groups at any time point during contraction. No difference in peak twitch force production existed between groups. However, at 3 min of stimulation, tension development was better maintained in the bicarbonate group (P<0.05), being ∼20% greater than control following 5 min of contraction (P<0.05). The results demonstrate, for the first time, that bicarbonate can augment acetyl group availability prior to contraction, independent of pyruvate dehydrogenase complex activation, but cannot influence the requirement for non-oxidative ATP re-synthesis during subsequent contraction. It would appear, therefore, that the bicarbonate-induced improvement in muscle tension development was probably mediated through the metabolic alkalosis and not via the increased availability of acetyl groups within the cell.

The purpose of the present study was to characterize the Ca2+ channels in smooth muscle cells from human stomach and to examine the effects of osmotic swelling on the channel activity. Ca2+ channel current with either Ca2+ or Ba2+ as charge carrier was recorded from freshly isolated smooth muscle cells using the conventional whole-cell patch clamp technique. The degree of cell swelling as a result of hypotonic challenge was monitored using a video image analysis system. The changes in intracellular Ca2+ concentration ([Ca2+]i) were measured by microfluorimetry. The pharmacological and voltage activation profile suggests a typical dihydropyridine-sensitive L-type Ca2+ current. Cell swelling, induced by hypotonic challenge, enhanced the amplitude of currents through L-type Ca2+ channels without significant effects on steady-state voltage dependency. After treatment with the L-type Ca2+ channel agonist Bay K 8644 (0.1-2 µM), no further significant increase in calcium channel current or corresponding [Ca2+]i transients were provoked by the swelling. The above results demonstrated that the presence of L-type Ca2+ current in smooth muscle cells of the human stomach and the augmentation of the current are closely associated with the volume increase resulting from hypotonic swelling. Experimental Physiology (2000) 85.5, 497-504.

In this investigation we have evaluated whether blockade of endothelin receptors influenced the renal haemodynamic and excretory responses to a period of ischaemia and reperfusion in the anaesthetised rat. The renal artery was occluded for 30 min and renal haemodynamic and excretory function followed for 90 min of reperfusion while either saline, the non-selective endothelin 1 receptor (ETA/ETB) antagonist SB209670 or the selective ETA receptor antagonist UK-350,926 was infused. In the post-ischaemic period, renal cortical and medullary perfusions were reduced by 40-50 %. When SB209670 was administered (30 µg kg-1 min-1 I.V.) for 30 min before, during and for 90 min after renal artery occlusion, cortical and medullary perfusions returned to baseline levels, responses different from those obtained during saline infusion (both P < 0.05). In the presence of UK-350,926 (30 µg kg-1 min-1 I.V.), perfusion in the medulla returned to baseline on clamp removal whereas that in the cortex remained depressed (P < 0.05). Renal ischaemia for 30 min decreased glomerular filtration rate during reperfusion and increased urine flow and sodium excretion 5- to 15-fold. UK-350,926 (30 µg kg-1 min-1 I.V.) reduced (P < 0.05) fluid excretion prior to ischaemia but during reperfusion, glomerular filtration rate returned to basal levels and there were progressive increases in fluid excretion which were smaller compared to the saline-treated group (all P < 0.05). The ischaemic challenge may cause release of endothelin, which acts on ETB receptors in the cortex and ETA receptors in the medulla to decrease perfusion. The blunted natriuresis and diuresis during blockade of ETA receptors may result from either a vascular or tubular action of endothelin. Experimental Physiology (2003) 88.4, 483-490.

Normal rats or rats parasympathetically denervated on one side by cutting the auriculo-temporal nerve were maintained on a liquid diet for 1 week. After fasting overnight, experimental rats were then offered hard, pelleted food over a period of 2 h, while unfed animals served as controls. The reflex-induced increase in the [3H]leucine incorporation into trichloroacetic acid-insoluble material of the parotid glands following intake of the food in the presence of the muscarinic blocker atropine and α- and β-adrenoceptor antagonists was greater (104 %) than in the absence of the blockers (75 %) in normal rats. The picture was the same when the innervated glands of rats subjected to unilateral parasympathetic denervation were examined. In this case, the protein synthesis increased by 108 % in the presence of the blockers and by 63 % in their absence. Analysis of the parasympathetically denervated and contralateral innervated glands revealed no support for a cholinergic or adrenergic contribution to this response. The increase in protein synthesis in the innervated glands was 86 % in the rats treated with atropine, whilst it was 76 % in those treated with α- and β-adrenoceptor antagonists. The protein synthesis in the denervated glands increased by 57 % in the absence of receptor blockade. Neither atropine (51 %), nor a- and b-adrenoceptor antagonists (52 %), nor a combination of the three blockers (55 %) affected the response of the denervated glands. A large part of the response in the presence of the traditional autonomic receptor blockers was thus dependent on the parasympathetic auriculo-temporal nerve. Under natural feeding conditions, the parasympathetic non-adrenergic, non-cholinergic (NANC) mechanisms are likely to contribute to the synthesis of secretory proteins. Experimental Physiology (2001) 86.5, 605-610.

The ability of the heart to function as an efficient pump is critically dependent on an adequate blood supply to the myocardium. When myocardial blood supply is reduced (ischaemia), contractile function of the heart is impaired and its cellular electrophysiological properties are profoundly altered. Prolonged ischaemia may result in cell necrosis which, if irreversible, leads to cell death (infarction) and predisposes the heart to ventricular arrhythmias, which in turn may be fatal. In man, myocardial ischaemia is the consequence of narrowing or occlusion of a coronary artery and is usually a manifestation of coronary artery disease which is often associated with thrombosis.

This study examined the effect of erythropoietin (EPO) on resting tension and on the responses of rat mesenteric and renal arcuate arteries in vitro to a number of agonists as a possible cause of its blood pressure elevating properties when used therapeutically. Noradrenaline and potassium chloride induced concentration-dependent vasoconstrictions in both vessel types but the basal tension, maximum tension, and the -log concentration producing half-maximal response (pEC50) were altered in the presence of 0·1 or 20 U ml-1 EPO. The thromboxane A2 receptor agonist U46619 induced a constriction of the renal arcuate arteries which was enhanced by EPO at 20 U ml-1, from 1·68 ± 0·34 to 2·64 ± 0·39 mN mm-1 (P < 0·01), but which was unchanged by NG-nitro-L-arginine methyl ester (10-4 m). Serotonin (10-9-10-5 M) caused a concentration-related vasoconstriction in renal arcuate arteries which was shifted to the right in the time control study (P < 0·001) but this was abolished by both 0·1 and 20 U ml-1 of EPO. Acetylcholine induced a relaxation of precontracted mesenteric arteries, by 95·4 ± 1·64 % with an EC50 of 7·08 ± 0·08 M which was reduced (P < 0·001) by 20 U ml-1 EPO to 81·7 ± 3·56 % and 6·10 ± 0·11 M, respectively. The sodium nitroprusside-induced relaxations were unaffected by EPO. The acetylcholine-mediated relaxations in renal arcuate arteries were unchanged by EPO. Bradykinin-induced relaxations in mesenteric and renal arcuate arteries were unaffected by both EPO concentrations. Together these data showed that EPO over a large concentration range had only minor effects on basal tension and the vascular responsiveness of both mesenteric and renal arcuate arteries. The mechanism whereby EPO causes a chronic elevation in blood pressure is unlikely to be due to acute interactions with agonist-mediated responses.

The effect of exposure to hypobaric hypoxia for 4 weeks (oxygen pressure = 106 hPa), equivalent to 5500 m in altitude) on myocardial total lactate dehydrogenase (tLDH) activity and isoform (H and M) composition was comparatively studied in growing (4.5 weeks old) and in adult (4.5 months old) male rats. The consequences of the hypoxia-induced anorexia were checked in growing rats using a pair-fed group. Exposure to hypoxia induced a significant decrease in the H/tLDH ratio in the left (LV) and right ventricle (RV) of growing and adult rats. In adult rats this alteration was mainly a consequence of the significant increase in the specific activity of the M isomer, which resulted in an increase in the overall LDH activity. In contrast, in the LV of young rats exposed to hypoxia, the specific activity of the M isomer was similar to that of normoxic animals while the H isomer activity was significantly lower than in normoxic rats, and the overall LDH activity remained unchanged. These effects were specifically due to hypoxia per se since no significant alterations were observed in pair-fed animals. In the hypertrophied RV, the alteration of H and M isomers following hypoxia was similar to that observed in adults (i.e. no change in H and an increase in M isoform). We conclude that the well-known hypoxia-induced decrease in the H/tLDH ratio is governed by different age-dependent mechanisms. In adult rats, hypoxia may induce in both ventricles a stimulating effect on M isomer expression. In the LV of growing rats this stress could inhibit the H isomer maturation without any effect on the M isomer. In the RV of growing rats this effect could have been counteracted by the growth effect of the hypertrophying process. Experimental Physiology (2003) 88.3, 405-413.

The effects of low-intensity, prolonged swimming on functional recovery of the rat heart (Langendorff preparations) from ischaemia-reperfusion (I/R) were investigated. Three groups of rats (120 days old) were used: sedentary rats (S) and rats exercised by a single bout of swimming lasting 5 (E5) or 8 h (E8), respectively. The effect of exercise on the response to I/R was related to an index of oxidative damage such as lipid peroxidation, as well as to the tissue antioxidant capacity and the response of heart tissue to in vitro oxidative stress. The intrinsic performance of E5 Langendorff preparations paced at 220 beats min-1 was also determined. A group of sedentary animals was used for H2O2-treated preparations. The effect of antioxidant treatment on inotropic recovery during reperfusion was studied on preparations from 5 or 8 h swimming vitamin E-treated (EVT5 and EVT8) and 5 or 8 h swimming untreated (EVU5 and EVU8) rats. Hearts from exercised animals displayed a reduced preischaemic inotropism, which in E5 rats was accompanied by an increase in the intrinsic heart rate. The lower intrinsic cardiac inotropism of E5 animals was confirmed in the paced preparations. The reduced contractility found in control hearts after addition of H2O2 to perfusion medium suggested that the low inotropism of E5 and E8 hearts was due to an exercise-induced increase in reactive oxygen species. Inotropic recovery during reperfusion was low in the S hearts, was significantly increased in the E5 hearts, and was again reduced to the S level in the E8 hearts. In the E8 hearts the indexes of cellular damage (LDH release) and oxidative stress increased, and antioxidant capacity decreased, while in E5 hearts there was no evidence of significant changes in such parameters. Performance and reperfusion recovery of hearts from 5 h swimming rats was not affected by vitamin E treatment, while those of hearts from 8 h swimming rats was the highest observed. We suggest that the higher inotropic recovery during reperfusion in the hearts from the E5 rats is related to the negative inotropic effect of exercise. The fall in recovery following the 8 h exercise was instead related to the increased oxidative stress. Experimental Physiology (2001) 86.3, 341-348.

The magnitude of diuresis and natriuretis produced by oxytocin in the female rat has been shown to be dependent on the stage of the oestrous cycle. A study has been performed to determine the role of ovarian steroids in modulating the renal response to oxytocin infused at a rate of 100 fmol min-1 in hypotonic saline. Observations were performed on ovariectomised rats with and without steroid treatment and rats with suppressed oestrous cycles following treatment with the long-acting gonadotrophin-releasing hormone analogue Zoladex, given as a 100 mg S.C. depot, or the antioestrogen tamoxifen, given as three daily injections of 1 mg. Steroid treatment comprised a single dose of 10 µg oestradiol benzoate or 2.0 mg progesterone, or a combination of the two hormones given 30 h apart. Ovariectomy had no significant effect on plasma oxytocin concentrations, although progesterone treatment produced an increase. The natriuresis in ovariectomised animals of 27 % was smaller (P < 0.05) than that seen on the day of pro-oestrus and closer to that seen in the intact rat at oestrus. The responses in animals with suppressed oestrous cycles following treatment with tamoxifen were not significantly different from those observed following ovariectomy, neither was the diuresis following Zoladex. The renal responses were greater following treatment with oestradiol than in the ovariectomised group. Thus ovarian steroids do influence the renal responsiveness to oxytocin with oestradiol augmenting the response.

The goal of the present study was twofold: (1) to detect the possible storage of dietary polyamines (PAs) in various tissues and (2) to investigate the role of dietary PAs in the differentiation of the pig intestinal epithelium. A first experimental series was designed to assess the accumulation of either milk PAs (mostly spermidine) or orally administered spermine (SPM) in piglet red blood cells (RBCs) and plasma, a preliminary stage in their distribution to growing and storage organs. Though PA concentrations of piglet RBCs and plasma were generally significantly higher than their sow counterparts, our experimental conditions failed to demonstrate that this increase could stem from ingested PAs. A second experimental series dealt with the determination of disaccharidase specific activities in proximal and distal parts of piglet gut on the 26th and 29th days after birth (preweaning time). In agreement with observations made previously on rat pups, we observed an increase in maltase specific activity (SA) at the end of the suckling period (the observed increase in sucrase SA was not significant). However, orally administered SPM did not affect this activity. Compared to the constant protein concentrations observed in both parts of the gut, the pancreatic protein content decreased sharply between the 26th and 29th postnatal days. At the same time pancreatic concentrations of spermidine (SPD) also decreased, suggesting that some pancreatic PAs were released as the organ secreted its proteins. In accordance with this hypothesis, we recorded SPM and SPD in pancreatic juice. The increases in PA concentrations seemed to follow the protein secretion pattern (i.e. PA concentrations reached a maximal value when the protein concentration was highest). The presence of PAs in pancreatic juice could be indicative of a control mechanism exerted by the pancreas on PA-induced growth and differentiation of porcine intestinal epithelium. Experimental Physiology (2000) 85.3, 301-308.

Previous studies have shown that central administration of GABA (gamma -aminobutyric acid), an inhibitory neurotransmitter, preferentially reduces hindquarters and carotid vascular resistances but not renal and coeliac vascular resistances in conscious rats. This study tested the hypothesis that these preferential actions of central GABA receptors are related to differences between vessels in resting autonomic vascular tone in freely moving rats. Rats were chronically implanted with intracisternal cannulas and/or electromagnetic probes to measure regional blood flows. In response to GABA administration, the changes in vascular resistance (arterial blood pressure/regional blood flow) of the hindquarters (n = 23) and carotid (n = 12) vascular beds were significantly and negatively correlated with basal vascular resistance. No such relationship was found for the renal (n = 21), coeliac (n = 13) and superior mesenteric (n = 23) vascular beds. This finding indicates that the responsiveness to GABA of brainstem pathways controlling the hindquarters and carotid vascular beds co-varies with resting resistance in hindquarters and carotid vessels. A similar analysis was performed, correlating the ongoing vascular resistance of each vessel with its response to ganglionic blockade by chlorisondamine. In this case, a significant negative correlation was also found for the hindquarters (n = 26) and carotid (n = 15) vascular beds, but not for the coeliac (n = 17) or superior mesenteric (n = 19) vessels. Together, these findings suggest that central GABA receptors accessible from the cisterna magna preferentially affect two vascular beds which, in the freely moving rat, show resting autonomic vascular tone. Experimental Physiology (2000) 85.5, 479-485.

The muscarinic agonist bethanechol was infused intravenously, under α- and β-adrenoceptor blockade, in anaesthetized rats at various dose levels (5-10, 20 and 40-50 µg kg-1 min-1) over 30 min. The amount of saliva secreted from the parotid gland was dose dependent at 95, 202 and 737µl, respectively. The salivary amylase activity was approximately the same at the two lower doses (506 U and 448 U, respectively), while it was higher (1268 U) at the highest dose. In response to the highest dose, but not to the lower doses, the total parotid glandular amylase activity and the numerical density of parotid acinar secretory granules were lowered, by 25 % and 22 %, respectively. Thus, in the rat parotid gland, agonists such as bethanechol, which use Ca2+ as a second messenger, may release proteins not only by non-granular mechanisms but also, and in contrast to the general belief, by granule exocytosis. Experimental Physiology (2002) 87.2, 147-152.

Exposure of human leukocytes to 12 % and 6 % O2in vitro resulted in striking ultrastructural and morphological changes. These changes included the appearance of crater-like holes, a reduction in granular size and disruption of the cellular membrane. The implications of these findings is discussed. Experimental Physiology (2000) 85.3, 263-266.

The exogenous application of GABA into the cisterna magna of the freely moving rat decreases hindquarters vascular tone as well as arterial pressure. GABA could influence GABA receptor subtypes A, B or C. However, the hindquarters vascular response to the stimulation of each receptor subtype has not yet been investigated. The present study therefore characterized the response to the GABAB receptor agonist baclofen injected into the cisterna magna of the conscious rat. Intracisternally injected baclofen induced long-lasting increases in hindquarters vascular resistance and arterial pressure in a dose-dependent manner. Both actions induced by baclofen were completely blocked by a prior intracisternal injection with the GABAB receptor antagonist CGP 35348 (p-[3-aminopropyl]-p-diethoxymethylphosphinic acid), and systemically by ganglionic blockade. These actions of baclofen were also abolished centrally by sodium pentobarbital anaesthesia. The results suggest that GABAB receptor stimulation via the cisterna magna induced hindquarters vasoconstriction, probably due to central disinhibition of sympathetic activity. Experimental Physiology (2003) 88.4, 491-496.