Intercellular communication between follicular angiotensin receptors and Xenopus laevis oocytes: medication by an inositol 1,4,5-trisphosphate-dependent mechanism.
In Xenopus laevis oocytes, activation of angiotensin II (AII) receptors on the surrounding follicular cells sends a signal through gap junctions to elevate cytoplasmic calcium concentration ([Ca2+]i) within the oocyte. The two major candidates for signal transfer through gap junctions into the oocyte during AII receptor stimulation are Ins(1,4,5)P3 and Ca2+. In [3H]inositol-injected follicular oocytes, AII stimulated two- to fourfold increases in phosphoinositide hydrolysis and production of inositol phosphates. Injection of the glycosaminoglycan, heparin, which selectively blocks Ins(1,4,5)P3 receptors, prevented both AII-stimulated and Ins(1,4,5)P3-induced Ca2+ mobilization in Xenopus follicular oocytes but did not affect mobilization of Ca2+ by ionomycin or GTP. These results indicate that the AII-regulated process of gap junction communication between follicular cells and the oocyte operates through an Ins(1,4,5)P3-dependent mechanism rather than through transfer of Ca2+ into the ooplasm and subsequent Ca(2+)-induced Ca2+ release.
Sandberg
K
K
Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892.
Ji
H
H
Iida
T
T
Catt
K J
KJ
D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002450:Cell Communication; D004305:Dose-Response Relationship, Drug; D005260:Female; D006493:Heparin / Q000494:pharmacology; D007294:Inositol / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007295:Inositol Phosphates / Q000302:isolation & purification / Q000378:metabolism; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D014982:Xenopus laevis
D007295:Inositol Phosphates; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D007294:Inositol; D015759:Ionomycin; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium