Angiotensin II and potassium activate different calcium entry mechanisms in rat adrenal glomerulosa cells.
Initial 45Ca uptake was measured in isolated rat glomerulosa cells. A small reduction in membrane potential produced by increasing the K+ concentration from 2 to 3.6 mmol/l stimulated 45Ca uptake by about 35%, while a bigger depolarization induced by 18.5 mmol K+/l increased the uptake by about 100%. Since Ca2+ influx was already activated at a calculated membrane potential below -70 mV, and was found to be sensitive to the dihydropyridine antagonist nifedipine (1 mumol/l), but insensitive to nickel ions (100 mumol/l), it does not meet the criteria established for T- or L-type voltage-dependent Ca2+ channels. Exposure of glomerulosa cells to angiotensin II (AII) for 10 min also enhanced the rate of 45Ca influx. The effect of AII was not sensitive to 1 mumol nifedipine/l, but was strongly inhibited by 5-(N-4-chlorobenzyl)-N-(2',4'-dimethyl)benzamil (CBDMB, 30 mumol/l), an inhibitor of the Na+/Ca2+ antiporter. These observations suggest that during the sustained phase of stimulation with AII, a CBDMB-sensitive mechanism, rather than dihydropyridine-sensitive calcium channels, is involved in Ca2+ uptake in rat glomerulosa cells. The bulk Ca2+ influx did not correlate with aldosterone production; however, the maintained activity of different Ca2+ entry mechanisms seems to be essential for AII-induced aldosterone production.
Spät
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A
Department of Physiology, Semmelweis University Medical School, Budapest, Hungary.
Balla
I
I
Balla
T
T
Cragoe
E J
EJ
Hajnóczky
G
G
Hunyady
L
L
D000450:Aldosterone / Q000378:metabolism; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger; D015384:Zona Glomerulosa / Q000187:drug effects / Q000378:metabolism*
D015220:Calcium Channels; D002352:Carrier Proteins; D008565:Membrane Proteins; D019831:Sodium-Calcium Exchanger; D000804:Angiotensin II; C054391:5-(N-4-chlorobenzyl)-N-(2',4'-dimethyl)benzamil; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium; D002118:Calcium