Acute effects of adenosine triphosphates, cyclic 3 ',5 '-adenosine monophosphates, and follicle-stimulating hormone on cytosolic calcium level in cultured immature rat Sertoli cells

The ability of ATP and FSH to induce intracellular calcium [Ca2+](i) change s in Sertoli cells is imperfectly understood and reports are conflicting. W e have applied the single-cell microfluorometry technique with the calcium probe indo-1 to investigate [Ca2+](i) in individual cultured Sertoli cells. When cells were exposed to ATP, cAMP, and FSH, a fast and biphasic increas e in [Ca2+](i) was obtained in 100%, 70%, and 56% of cells, respectively. C affeine did not activate Ca2+ mobilization, while thapsigargin suppressed t he peak response. External calcium free-EGTA buffer suppressed the plateau phase, while blockers of voltage-operated Ca2+ channels did not abolish the response to cAMP and ATP. We conclude that the three messengers mobilized Ca2+ from intracellular thapsigargin-sensitive stores, which induced a subs equent Ca2+ influx from the extracellular medium by a voltage-independent C a2+ entry. The well-documented mechanisms by which these messengers act on cells support the idea that they release Ca2+ from smooth endoplasmic retic ulum by two different pathways, or that FSH and cAMP first release ATP, whi ch then acts on cells. Among the cells, 77% and 80% responded, respectively , to FSH and cAMP by a delayed longlasting decrease in [Ca2+](i) that was n ever recorded in the presence of ATP. This suggests that FSH and cAMP also promote a slow redistribution of [Ca2+](i) from the exchangeable pool to th e bound nonexchangeable pools. Involvement of voltage-operated and voltage- independent calcium channels in the response of Sertoli cells to ATP, FSH, and cAMP is discussed.