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.

Abstract

Cytosolic [Ca2+]i was measured using a microspectrofluorimetric technique. Prostaglandin F2 alpha (PGF2 alpha, 10(-6) M) transiently increased the concentration of free cytosolic Ca2+ ([Ca2+]i) in individual rat and human granulosa cells. In a study examining a total of 170 individual rat and human granulosa cells, approximately 100% of rat granulosa cells and 80% of human granulosa cells tested responded to PGF2 alpha (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 (10(-4) to 10(-6) M) did not affect [Ca2+]i in rat or human granulosa cells. GnRH (10(-6) M) increased [Ca2+]i in rat but not human granulosa cells. Over 90% of rat granulosa cells tested responded. Angiotensin II (ANG II, 10(-5) M) increased [Ca2+]i in approximately 25% of rat, but not human granulosa cells. Individual rat granulosa cells which responded to GnRH responded to PGF2 alpha and vice versa. Individual rat granulosa cells which responded to ANG II responded to PGF2 alpha and GnRH. 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 perifusion suggested that effects of PGF2 alpha, GnRH, and ANG II on [Ca2+]i were receptor specific. However, the effects of combined hormone treatments 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 this study suggested that effects of PGF2 alpha, GnRH, and ANG II receptor-ligand interactions may be at least partially mediated by transient increases in [Ca2+]i in rat granulosa cells. Similarly, effects of PGF2 alpha, but not GnRH or ANG II, receptor-ligand interactions may be mediated by transient increases in [Ca2+]i in human granulosa cells.