Dependency of phorbol ester-induced gonadotropin secretion on estradiol.
Phorbol 12-myristate 13-acetate (PMA), which activates protein kinase C (PKC) was used to investigate the estradiol dependency of PKC-stimulated luteinizing hormone (LH) secretion from perifused anterior pituitaries. Infusions of PMA stimulated LH secretion from diestrous II, ovariectomized + estradiol-treated, and orchidectomized + estradiol-treated quartered pituitaries, by protein synthesis-dependent mechanisms. In contrast, pituitaries from intact, orchidectomized males, or ovariectomized females were unresponsive to PMA. Interestingly, dispersed male pituitary cells differed from male pituitary tissue blocks, in that the dispersed cells responded to PMA with increased LH secretion. These results indicate that PKC's ability to directly stimulate LH secretion is dependent on de novo protein synthesis and estradiol. Moreover, the effects of estradiol on PKC-stimulated secretion form at least one basis for the estradiol-induced increased responsiveness of gonadotrophs to GnRH. Additionally, it appears that dispersed pituitary cells may not respond to activators of PKC in a physiological manner.
Fahmy
N W
NW
Department of Physiology, University of Alberta, Edmonton, Canada.
Das
S
S
Bourne
G A
GA
D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004031:Diestrus / Q000378:metabolism; D004958:Estradiol / Q000502:physiology*; D005260:Female; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010906:Pituitary Hormone-Releasing Hormones / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D006065:Gonadotropins, Pituitary; D010906:Pituitary Hormone-Releasing Hormones; D004958:Estradiol; D003513:Cycloheximide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate