Capacitative Ca(2+) entry into bovine adrenocortical fasciculata cells was investigated by using the mobilization of intracellular Ca(2+) concentration ([Ca(2+)](i)) and Ca(2+)-induced steroidogenesis as the indicators. Bovine adrenocortical fasciculata cells on a glass coverslip were loaded with fura-2. The [Ca(2+)](i) mobilization was detected by a change of fura-2 fluorescence intensity. In the intracellular Ca(2+) store depleted cells, the addition of Ca(2+) to the incubation medium elicited a marked and sustained increase in [Ca(2+)](i). In the intracellular Ca(2+) store non-depleted cells, the addition of thapsigargin, an endoplasmic reticulum Ca(2+)-ATPase inhibitor, in the absence of extracellular Ca(2+), induced a slight and transient increase in [Ca(2+)](i), but an extensive and sustained increase in [Ca(2+)](i) was obtained by adding Ca(2+) to the incubation medium after the thapsigargin treatment. The sustained increase induced by thapsigargin was not inhibited by nifedipine, but was inhibited by Zn(2+) and Cd(2+) in a concentration-dependent manner. The effect of Zn(2+) was more potent than that of Cd(2+). Thapsigargin stimulated steroidogenesis in the presence of extracellular Ca(2+). The steroidogenic effect of thapsigargin was inhibited by Zn(2+) and Cd(2+) but not by nifedipine. These results suggest that there is, in bovine adrenocortical fasciculata cells, a steroidogenesis-linked Ca(2+) entry process other than that involving voltage-operated Ca(2+) channels and that the process might be capacitative Ca(2+) entry.

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