Biology of Reproduction, Vol 52, 721-728, Copyright © 1995 by Society for the Study of Reproduction

ARTICLES

Influence of the muscarinic agonist carbachol on intracellular Ca2+ in chicken granulosa cells: I. Dependence on follicular maturation

J Soboloff, MG Wade, G Wells, M Desilets and BK Tsang
Reproductive Biology Unit, Loeb Medical Research Institute, Ottawa Civic Hospital, Ontario, Canada.

The present study addressed the influence of follicular development on carbamylcholine chloride (Cch)-induced Ca2+ transients and inositol 1,4,5-trisphosphate (IP3) production in granulosa cells isolated from the first (F1), third (F3), and fifth and sixth (F5,6) largest follicles. Intracellular free calcium, [Ca2+]i, was measured in fura-2- loaded cells about 20-36 h after their isolation. The percentage of cells responding to a maximal stimulatory concentration of Cch (0.2 mM) was higher in the F1 (89%) granulosa cells than in cells from the F3 (68%) and the F5,6 (72%) follicles. Most of the Ca2+ transients that were elicited in F1 granulosa cells were characterized by large (696 +/- 119 nM), fast (260 +/- 55 nM/sec) increases in [Ca2]i followed by a slow, uneven decrease in [Ca2+]i to the resting concentration. In contrast, Cch-induced changes in [Ca2+]i in F3 and F5,6 granulosa cells were generally both smaller (154 +/- 37 nM and 165 +/- 37 nM, respectively) and slower (36 +/- 25 nM/sec and 46 +/- 16 nM/sec, respectively) than those observed in cells from the largest follicle. Removal of external Ca2+ did not alter the large, fast increases in [Ca2+]i; however, it nearly blocked the slow responses observed in F3 and F5,6 cells. IP, production was elevated in 3H-myo-inositol-loaded F1 granulosa cells after 1 min of Cch (0.2 mM) treatment, whereas inositol bisphosphate (IP2) production and inositol monophosphate (IP) production were elevated only after longer incubations.(ABSTRACT TRUNCATED AT 250 WORDS)