Rat oocyte maturation: role of calcium in hormone action.
We studied the role of extracellular calcium (Ca0) in oocyte maturation and oocyte-cumulus cells interaction in rat follicles in vitro. Luteinizing hormone (LH) or a gonadotropin-releasing hormone analog (GnRHa) induced full maturation at [Ca0] = 1.3 mM. At [Ca0] = 0.6 mM, maturation induced by LH or GnRHa was inhibited by 65%. Chelatin of [Ca0] resulted in 45% maturation and neither hormone caused a further increase of maturation. [Ca0] = 20 mM enhanced the response to suboptimal concentrations of GnRHa but inhibited that to LH. Divalent cation ionophores caused [Ca0]-dependent maturation, which was fully inhibited by dibutyryl cAMP. Changes in [Ca0] also affected oocyte-cumulus interaction. At [Ca0] = 1.3 mM, either LH or GnRHa caused partial dispersion of the cumulus. Chelation of [Ca0] also resulted in an almost complete dispersion of the cumulus. The ionophores, however, caused maturation with the oocyte-cumulus complex preserved intact. Our data suggest that GnRHa may induce maturation via cAMP-sensitive calcium mobilization into the oocyte-cumulus-granulosa complex.
Goren
S
S
Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel.
Oron
Y
Y
Dekel
N
N
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D015759:Ionomycin / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D051381:Rats; D011919:Rats, Inbred Strains
D015220:Calcium Channels; D000001:Calcimycin; D004533:Egtazic Acid; D015759:Ionomycin; D003994:Bucladesine; D007986:Luteinizing Hormone; D002118:Calcium