Diversity in responses from endogenous and expressed mammalian receptors which cause chloride ion efflux from ovarian follicles of Xenopus laevis.
Inositol phosphates are produced in ovarian follicles of Xenopus laevis on activation of endogenous acetylcholine receptors, which also stimulates Ca2+ release and efflux of Cl- ions detected electrophysiologically. Inositol phosphates were not detectable on activation of endogenous angiotensin II receptors which did, however, stimulate both a dose-dependent Ca2+ efflux and a depolarizing current very similar in maximum size and other characteristics to those caused by acetylcholine action. In contrast, activation of exogenous receptors for angiotensin II expressed by microinjected mRNA extracted from bovine adrenal did form measurable inositol phosphates. Also, the endogenous electrophysiological responses to angiotensin II and acetylcholine desensitize homologously but fail to cross-desensitize (Lacy, McIntosh, and McIntosh, 1989, Biochem. Biophys. Res. Commun, 159, 658-663). It appears that endogenous ovarian angiotensin II receptors in Xenopus activate a different transduction mechanism from endogenous acetylcholine receptors and expressed mammalian adrenal angiotensin II receptors and/or may be sited in the electrically connected follicular cells rather than in the oocyte itself.
McIntosh
R P
RP
Department of Obstetrics and Gynaecology, Wellington School of Medicine, University of Otago, New Zealand.
McIntosh
J E
JE
D000109:Acetylcholine / Q000494:pharmacology*; D000311:Adrenal Glands / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002712:Chlorides / Q000378:metabolism*; D004594:Electrophysiology / Q000379:methods; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D006080:Ovarian Follicle / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D011945:Receptors, Angiotensin / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D014982:Xenopus laevis
D002712:Chlorides; D007295:Inositol Phosphates; D012333:RNA, Messenger; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D000109:Acetylcholine; D002118:Calcium