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Changes in intracellular content of glutathione and thiols associated with γ-glutamyl cycle during sperm penetration and pronuclear formation in rat oocytes

Published online by Cambridge University Press:  01 November 1999

Hiroaki Funahashi
Affiliation:
Department of Animal Science and Technology, Faculty of Agriculture, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
Naoya Bandoh
Affiliation:
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
Shinobu Nakahira
Affiliation:
Department of Animal Science and Technology, Faculty of Agriculture, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
She-Hoon Oh
Affiliation:
Department of Animal Science and Technology, Faculty of Agriculture, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
Seiji Tsuboi
Affiliation:
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.

Abstract

The content of glutathione and other thiols in rat eggs was examined during sperm penetration and pronuclear formation by high-performance liquid chromatography with fluorescence detection. Reduced glutathione (GSH) content was higher in unfertilised oocytes (8.50 ± 0.29 pmol/egg) and penetrated eggs with a decondensed sperm nucleus (DSH eggs; 7.72 ± 0.56 pmol/egg) than eggs at the pronuclear stage (PN eggs; 5.93 ± 0.10 pmol/egg). The content of oxidised glutathione (GSSG) was not different among experimental groups (152.6 ± 74.1 nmol/egg in unfertilised eggs, 146.0 ± 50.0 nmol/egg in DSH eggs and 39.7 ± 17.3 nmol/egg in PN eggs). The GSSG/GSH ratio did not change during fertilisation. Although the reduced cysteinylglycine content of eggs did not change among experimental groups, the oxidised form of cysteinylglycine increased (p < 0.025) between sperm decondensation (6.9 ± 1.5 nmol/egg in unfertilised oocytes and 10.1 ± 2.1 nmol/egg in DSH eggs) and pronuclear formation (40.5 ± 11.5 nmol/egg in PN eggs). Low contents of cystine were detected during fertilisation but cysteine and γ-glutamylcysteine were not detected in any treatment groups. These results demonstrate that GSH content in rat eggs decreases between sperm decondensation and pronuclear formation, probably due to the increased activity of γ-glutamyl transpeptidase.

Type
Research Article
Copyright
1999 Cambridge University Press

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