CYTOSOLIC FREE CALCIUM INCREASED BY PROSTAGLANDIN-F2-ALPHA (PGF2-ALPHA), GONADOTROPIN-RELEASING-HORMONE, AND ANGIOTENSIN-II IN RAT GRANULOSA-CELLS AND PGF2-ALPHA IN HUMAN GRANULOSA-CELLS

Cytosolic [Ca2+]i was measured using a microspectrofluorimetric techni que. Prostaglandin F2-alpha (PGF2-alpha, 10(-6) M) transiently increas ed the concentration of free cytosolic Ca2+ ([Ca2+]i) in individual ra t and human granulosa cells. In a study examining a total of 170 indiv idual rat and human granulosa cells, approximately 100% of rat granulo sa cells and 80% of human granulosa cells tested responded to PGF2-alp ha (10(-6) M). In a dose-response trial, the magnitude of the [Ca2+]i response did not vary, although a decreasing number of cells responded to decreasing PGF2-alpha concentrations (10(-5) to 10(-9) M). PGE2 (1 0(-4) to 10(-6) M) did not affect [Ca2+]i in rat or human granulosa ce lls. GnRH (10(-6) M) increased [Ca2+]i in rat but not human granulosa cells. Over 90% of rat granulosa cells tested responded. Angiotensin I I (ANG II, 10(-5) M) increased [Ca2+]i in approximately 25% of rat, bu t not human granulosa cells. Individual rat granulosa cells which resp onded to GnRH responded to PGF2-alpha and vice versa. Individual rat g ranulosa cells which responded to ANG II responded to PGF2-alpha and G nRH. Conversely, less than 30% of individual rat granulosa cells which responded to PGF2-alpha and GnRH responded to ANG II. Desensitization (pretreatment) of rat granulosa cells by continuous hormone perifusio n suggested that effects of PGF2-alpha, GnRH, and ANG II on [Ca2+]i we re receptor specific. However, the effects of combined hormone treatme nts on [Ca2+]i were not additive. The transient increase in [Ca2+]i in response to PGF2-alpha or GnRH, alone, may be maximal. Results of thi s study suggested that effects of PGF2-alpha, GnRH, and ANG II recepto r-ligand interactions may be at least partially mediated by transient increases in [Ca2+]i in rat granulosa cells. Similarly, effects of PGF 2-alpha, but not GnRH or ANG II, receptor-ligand interactions may be m ediated by transient increases in [Ca2+]i in human granulosa cells.