Effect of prostaglandin F2 alpha on cytosolic free calcium ion concentrations in rat luteal cells.

Changes in cytosolic free calcium concentrations [( Ca2+]i) in response to prostaglandin F2 alpha (PGF2 alpha) were measured in single rat luteal cells, using the calcium-sensitive fluorescent dye fura-2. A total of 112 cells were studied in 20 experiments. The average resting [Ca2+]i was 113 +/- 6.4 nM. In 59 cells (53%), there was a 4.6 +/- 0.2-fold increase in [Ca2+]i within 29.3 +/- 1.0 sec of PGF2 alpha administration, and the cells recovered by 78.0 +/- 4.5 sec. The magnitude of the increase in [Ca2+]i in response to PGF2 alpha was not changed by an increase in the concentration of PGF2 alpha. Perifusion with low calcium buffer reduced, then eliminated, the [Ca2+]i response to PGF2 alpha. Perifusion of cells with PGF2 alpha resulted in a single transient [Ca2+]i response, similar to that after short term exposure to PGF2 alpha. Many (67%) of the cells that responded to PGF2 alpha also responded to GnRH. No additive increase in [Ca2+]i was seen when PGF2 alpha and GnRH were administered together. The source of the calcium appears to be intracellular stores that are shared by GnRH and PGF2 alpha.