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Luteinizing Hormone-Induced Intracellular Calcium Mobilization in Granulosa Cells: Comparison with Forskolin and 8-Bromo-Adenosine 3′,5′-Monophosphate*

1987; Oxford University Press; Volume: 120; Issue: 3 Linguagem: Inglês

10.1210/endo-120-3-853

1945-7170

Elikplimi K. Asem, Miklós Molnár, F. Hertelendy,

Rabbits: Nutrition, Reproduction, Health

Digitonin-permeabilized avian granulosa cells were used as a model to study the effects of LH, 8-bromo-cAMP (8-Br-cAMP), and forskolin on intracellular calcium mobilization. LH caused a biphasic calcium efflux. There was a small but significant (P < 0.05) calcium release within 1–2 min (rapid phase) with an ED50 of 35 μg/ml, followed by a larger one after 5 min (slow phase) with an ED50 of 10 ng/ml. The intracellular calcium antagonist TMB-8 inhibited the action of LH in both phases. Forskolin had no effect on calcium efflux during the rapid phase. However, it stimulated intracellular calcium efflux in a dose-dependent manner in the slow phase with an ED60 of 30 fiM. Low doses of 8-Br-cAMP caused a small but significant increase in calcium uptake corresponding to the rapid phase, although high concentrations of 8-Br-cAMP caused efflux in the slow phase (ED50) 0.7 mM). Both LH and 8-Br-cAMP mobilized calcium from a nonmitochondrial pool, whereas forskolin induced calcium efflux from a nonendoplasmic reticular site. Apparently receptor-mediated (LH) and nonreceptor-mediated (forskolin and 8-Br-cAMP) intracellular calcium mobilization are qualitatively different, suggesting that rapid intracellular calcium mobilization may represent one of the initial steps in the mechanism of action of LH. (Endocrinology120: 853–859, 1987)