Antioxidants reversibly inhibit the spontaneous resumption of meiosis

We previously showed that the cell-permeant antioxidant 2(3)-tert-butyl-4-h ydroxyanisole (BHA) inhibited germinal vesicle breakdown (GVBD) in oocyte-c umulus complexes (OCC) of the rat. The objective of the present studies was to assess other antioxidants and whether such inhibition was reversible. S pontaneous GVBD in OCC incubated for 2 h was significantly inhibited (P < 0 .005) by nordihydroguaiaretic acid (NDGA; GVBD = 19.4%), BHA (GVBD = 25.7%) , octyl gallate (OG; GVBD = 52.2%), ethoxyquin (EQ; GVBD = 58.88), 2,6-di-t ert-butyl-hydroxymethyl phenol (TBHMP; GVBD = 59%), butylated hydroxytoluen e (BHT; GVBD = 59.5%), and tert-butyl hydroperoxide (TBHP; GVBD = 60.0%). O ther antioxidants that produced lower but significant (P < 0.05) inhibition of oocyte maturation included propyl gallate (PG; GVBD = 70.3%), 2,4,5-tri hydroxybutrophenone (THBP; GVBD = 71.4%), and lauryl gallate (LG; GVBD = 71 .4%). Antioxidants that had no effect on oocyte maturation at the same conc entration (100 mu M) included ascorbic acid, vitamin E, and Trolox. Inhibit ion of GVBD was evident for up to 8 h of incubation of OCC and denuded oocy tes (DO) with BHA. or NDGA and was reversed by washing. NDGA was less poten t than BHA for inhibition of GVBD in DO, unlike that seen with OCC. Oocyte maturation was induced by incubation of follicles for 3 h with human chorio nic gonadotropin (hCG), and this response was inhibited by BHA or NDGA. The se findings support the conclusion that cell-permeant antioxidants inhibit spontaneous resumption of meiosis, which may implicate a role of oxygen rad icals in oocyte maturation.