Dihydropyridine-sensitive initial component of the ANG II-induced Ca2+ response in rat adrenal glomerulosa cells.
The Ca2+ signal induced by an increase in extracellular K+ concentration from 3.6 to 5.6 mM or angiotensin II (ANG II) was inhibited by the dihydropyridine (DHP) Ca2+ channel blocker, nifedipine, and enhanced by the DHP Ca2+ channel agonist, BAY K 8644. The DHP sensitivity of the ANG II-induced Ca2+ response was already detectable during the peak phase, suggesting that the DHP receptor plays an important role during the initial phase of ANG II stimulation. K+ and ANG II stimulated a nifedipine-sensitive Mn2+ influx pathway, further promoting the role of a DHP receptor in their mechanism of action. Fluorescent membrane potential measurements showed that, in contrast to the rapid depolarization induced by K+, the ANG II-induced depolarization had a lag time of > 30 s. The slow kinetics of depolarization compared with the immediate effect of ANG II on Mn2+ influx and the DHP sensitivity of the initial Ca2+ peak indicates that ANG II initiates the activation of the DHP-sensitive Ca2+ channel by a mechanism other than depolarization.
Hunyady
L
L
Department of Physiology, Semmelweis University of Medicine, Budapest, Hungary.
Rohács
T
T
Bagó
A
A
Deák
F
F
Spät
A
A
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines / Q000494:pharmacology*; D005260:Female; D008345:Manganese / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009124:Muscle Proteins / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015384:Zona Glomerulosa / Q000166:cytology / Q000187:drug effects*
D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; D009124:Muscle Proteins; D000804:Angiotensin II; D008345:Manganese; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine; D009543:Nifedipine; D011188:Potassium; D002118:Calcium