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.