Abstract: BACKGROUND AND AIM: To investigate the effects of thioglycolic acid (TGA) on the nuclear status during progesterone-induced in vitro Xenopus oocyte maturation. MATERIALS AND METHODS: Xenopus oocytes were treated with TGA in vitro at doses of 0, 5, 25 and 125 μg/ml. Germinal vesicle breakdown (GVBD) was checked during culture. Oocytes collected at 8 h were stained with hoechst 33258 to evaluate the chromosome status. RESULTS: Obvious early occurrence of GVBD was found in TGA-treated Xenopus oocytes, as indicated by GVBD50 (time to which 50％ of the oocytes underwent GVBD) and comparison was significant(P<0.05). In immunofluorescence-stained oocytes, no condensed chromosome was seen at GV phase, but metaphase plate was formed at MI phase and metaphase plate and the first polar body(PB1)were all observed at MII phase. However, there were lower MI-MII transition rates and PB1 extrusion rates in TGA-treated groups as compared with control(P<0.05). CONCLUSION: TGA treatment could inhibit Xenopus oocyte maturation as indicated by MI-MII transition, despite GVBD was accelerated by TGA.

Key words: thioglycolic acid, oocytes, maturation