Prostaglandin F2 alpha and gonadotropin-releasing hormone increase intracellular free calcium in rat granulosa cells.
Changes in cytosolic free calcium concentration ([Ca2+]i) in response to prostaglandin F2 alpha (PGF2 alpha) and gonadotropin-releasing hormone (GnRH) were measured in single rat granulosa cells, using the calcium-sensitive fluorescent dye, fura-2AM. In 90 out of 135 granulosa cells (67%), there was a 3- to 4-fold increase in resting [Ca2+]i within 30 s of administration of PGF2 alpha (10(-6) M). The resting [Ca2+]i returned to pre-stimulation levels in approximately 80 s. Granulosa cells were responsive to PGF2 alpha at concentrations ranging from 10(-7) M to 10(-4) M (n = 7). Within this range of concentrations, the magnitude of the calcium response did not differ. In another series of experiments, the majority (93%, n = 57) of the granulosa cells which responded to PGF2 alpha also responded to GnRH. Neither the magnitude of the [Ca2+]i response nor the time to response differed between PGF2 alpha and GnRH. Furthermore, simultaneous treatment of granulosa cells with both hormones did not generate a larger response than with either hormone alone. During perifusion with low calcium media, the characteristic [Ca2+]i response to PGF2 alpha decreased, and was eliminated within 10 min (n = 9). Similar observations were made in response to GnRH under these conditions. These data confirm that PGF2 alpha and GnRH stimulate a transient increase in [Ca2+]i in rat granulosa cells, the source of which may be shared intracellular stores.
Rodway
M R
MR
Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, Canada.
Steele
G L
GL
Baimbridge
K G
KG
Leung
P C
PC
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000378:metabolism*; D066298:In Vitro Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost; D002118:Calcium