Capacitative Ca2+ influx in adrenal glomerulosa cells: possible role in angiotensin II response.
We examined the effect of the depletion of intracellular Ca2+ stores on Ca2+ influx in rat glomerulosa cells. Depletion of intracellular Ca2+ stores was achieved by inhibiting sarco/endoplasmic reticulumtype Ca(2+)-ATPase with thapsigargin or 2,5,di-(t-butyl)-1,4-benzohydroquinone (t-BHQ). Both inhibitors induced a sustained rise in cytoplasmic Ca2+ concentration. The initial rise was observed also in Ca(2+)-free medium, while the sustained phase disappeared, indicating that the latter requires Ca2+ influx. In Ca(2+)-free medium, the readdition of Ca2+ induced a steeper and higher rise in intracellular Ca2+ concentration in thapsigargin-treated cells than in controls, supporting the role of Ca2+ influx. In normal medium, the addition of Cd2+ (80 microM) evoked an immediate inhibition of the sustained phase of thapsigargin response. The response to thapsigargin was insensitive to nifedipine. Thapsigargin failed to enhance Mn2+ quenching of fura 2. Our results provide evidence for the existence of capacitative Ca2+ influx in rat glomerulosa cells and indicate that dihydropyridine-sensitive Ca2+ channels do not participate in capacitative Ca2+ entry. High concentrations of thapsigargin and t-BHQ, similar to the reported effects of angiotensin II and vasopressin, inhibited K(+)-induced Ca2+ signals. These effects appear, however, to be independent of the depletion of internal Ca2+ stores.
Department of Physiology, Semmelweis University of Medicine, Budapest, Hungary.
T
T
Rohács
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A
Bagó
F
F
Deák
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L
Hunyady
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A
Spät
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D016257:Fura-2; D006873:Hydroquinones / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D009994:Osmolar Concentration; D011188:Potassium / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D015384:Zona Glomerulosa / Q000166:cytology / Q000378:metabolism*
D006873:Hydroquinones; D013729:Terpenes; D000804:Angiotensin II; D008345:Manganese; D019284:Thapsigargin; C018855:2-tert-butylhydroquinone; D000252:Calcium-Transporting ATPases; D009543:Nifedipine; D011188:Potassium; D002118:Calcium; D016257:Fura-2