Luteinizing hormone but not endothelin can induce a calcium signal in the chicken granulosa cell

Using the fluorescent calcium-indicator Indo-1 we demonstrated a rapid transient increase of cytosolic calcium level in dispersed chicken granulosa cells in response to 10-100 ng/ml ovine luteinizing hormone (LH). The magnitude of the signal was dose-dependent, it lasted for about 30 seconds and could be provoked even when the extracellular calcium had been chelated by EGTA. A high, 100 ng/ml concentration of LH abolished completely the responsiveness of these cells to a second exposure to the agonist. We conclude, that LH can mobilize calcium ions from internal store(s) via a desenzitizable mechanism. Finally, endothelin--a vasoactive peptide with Ca2(+)-mobilizing activity in glomerulosa cells--was shown to have no effect on the concentration of cytosolic Ca2+ in chicken granulosa cells.