Capacitative calcium entry is involved in steroidogenesis in bovine adrenocortical fasciculata cells.
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.
Ebisawa
T
T
Department of Pharmacology (I), Jikei University School of Medicine, 3-25-8 Nishi-Shinbashi, Minato-ku, Tokyo 105-8461, Japan.
Kondo
I
I
Masaki
E
E
Hori
S
S
Kawamura
M
M
D000704:Analysis of Variance; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D006854:Hydrocortisone / Q000096:biosynthesis*; D007424:Intracellular Fluid / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009543:Nifedipine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology; D015383:Zona Fasciculata / Q000166:cytology / Q000378:metabolism*
D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D002104:Cadmium; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D009543:Nifedipine; D015032:Zinc; D002118:Calcium; D016257:Fura-2; D006854:Hydrocortisone