Opening of glibenclamide-sensitive K+ channels in follicular cells promotes Xenopus oocyte maturation.
The vasorelaxing K+ channel opener P1060 (a pinacidil analog), gonadotropins, and cAMP were shown to activate a glibenclamide-sensitive 86Rb+ efflux from fully grown follicle-enclosed Xenopus oocytes. Glibenclamide-sensitive K+ channels are located in follicular cells. Glibenclamide (i) depressed the gonadotropin- but not the progesterone-induced maturation and (ii) did not significantly modify progesterone production in oocytes exposed to Xenopus gonadotropin. In follicle-enclosed oocytes, the opener P1060 very significantly enhanced the oocyte sensitivity to progesterone. This increased sensitivity to the hormone induced by the K+ channel opener was reversed by glibenclamide. Thus these results suggest that the opening of glibenclamide-sensitive K+ channels in follicular cells by gonadotropins (and other activators of this channel) induces a hyperpolarization in the oocyte that greatly facilitates maturation by increasing the oocyte sensitivity to progesterone.
Wibrand
F
F
Centre National de la Recherche Scientifique, Université de Nice-Sophia Antipolis, Valbonne, France.
Honoré
E
E
Lazdunski
M
M
D000818:Animals; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D008540:Meiosis / Q000187:drug effects; D009866:Oogenesis; D006080:Ovarian Follicle / Q000502:physiology*; D010907:Pituitary Hormones / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology / Q000502:physiology; D014982:Xenopus laevis / Q000502:physiology*
D010907:Pituitary Hormones; D015221:Potassium Channels; D011374:Progesterone; D005905:Glyburide