Functional alteration of dihydropyridine-sensitive Ca(2+) channels in the adrenal glomerulosa of pregnant rats.
Our previous work on aldosterone secretion suggested that dihydropyridine-sensitive calcium channels, one type of voltage-dependent calcium channels (VDCC), are functionally impaired in adrenal capsule preparations from the pregnant rat. The aim of this study was to determine whether, during pregnancy, the density and/or activity of these channels is altered in the adrenal zona glomerulosa. These VDCC measured with [(3)H]nitrendipine binding were not different between membrane preparations of nonpregnant and pregnant rats. Western blots were performed using two different antibodies, a polyclonal (PcAb) directed against the alpha(1)-subunit of VDCC and a monoclonal (McAb) that recognizes an intracellular domain of that protein. McAb immunoreactivity showed a significant decrease in preparations from pregnant rats, whereas no difference was observed with PcAb. VDCC activity was estimated by (45)Ca(2+) uptake in isolated adrenal cortex and by intracellular calcium concentration ([Ca(2+)](i)) in adrenal glomerulosa cells with the Ca(2+) probe fura PE3. These measurements revealed that KCl stimulation produced greater Ca(2+) influx in nonpregnant than in pregnant rats. Nifedipine (a blocker of VDCC) inhibited this stimulation only in nonpregnant rats, whereas BAY K 8644 (an activator of VDCC) increased Ca(2+) influx in pregnant rats only. These data suggest that, during pregnancy, the altered regulation of calcium homeostasis in adrenal glomerulosa is linked to a conformational alteration of VDCC.
Simaan
M
M
Research Center, Hôpital Ste-Justine, and the Department of Obstetrics-Gynaecology, Université de Montréal, Montreal, QC, Canada H3T 1C5.
Picard
S
S
St-Louis
J
J
Brochu
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology*; D002132:Calcium Radioisotopes / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D009543:Nifedipine / Q000494:pharmacology; D009568:Nitrendipine / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014316:Tritium; D014700:Verapamil / Q000494:pharmacology; D015384:Zona Glomerulosa / Q000187:drug effects / Q000502:physiology*
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002132:Calcium Radioisotopes; D014316:Tritium; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009568:Nitrendipine; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium