Capacitative calcium entry in rat Sertoli cells

Abstract

Depletion of intracellular Ca2+ stores activates an influx of Ca2+ from the extracellular medium. This capacitative Ca2+ entry as originally proposed by Putney in 1986 can be studied with drugs that inhibit sarco/endoplasmic reticulum ATPase. In the present study we examined the effects of depletion of internal Ca2+ stores on Ca2+ influx in rat Sertoli cells utilizing thapsigargin and cyclopiazonic acid. Both inhibitors induced a rapid and dose-dependent rise in [Ca2+]i that was dependent on an influx of Ca2+ from the extracellular medium since it was rapidly blocked by the addition of the Ca2+ chelating agent EGTA. In the absence of external Ca2+ thapsigargin and cyclopiazonic acid still produced an increase in [Ca2+]i that was lower than that observed in Ca2+ medium and was transient since [Ca2+]i returned to basal levels by few minutes. In these experimental conditions readdition of Ca2+ induced a rapid rise in [Ca2+]i supporting a role for Ca2+ influx. Increase of plasma membrane permeability to Ca2+ induced by thapsigargin and cyclopiazonic acid were confirmed by the ability of Mn2+ to permeate through Ca2+ channels and to quench intracellular fura-2 fluorescence after challenge with these inhibitors. Mn2+ induced influx was blocked by La3+, a well known blocker of Ca2+ channels. These results demonstrate that internal Ca2+ stores depletion induce Ca2+ influx from the extracellular medium in rat Sertoli cells providing evidence for the existence of capacitative Ca2+ entry in these cells.