Modulation of the dihydropyridine-insensitive Ca2+ influx by 8-bromo-guanosine-3':5'-monophosphate, cyclic (8-Br-cGMP) in bovine adrenal chromaffin cells.
Pretreatment of chromaffin cells with the permeable analogue of cGMP, 8-Br-cGMP (100 microM), leads to a reduction (35%) of depolarization-evoked intracellular calcium concentration ([Ca2+]i) increases. There is evidence that bovine adrenal chromaffin cells are provided with both dihydropyridine-sensitive and -resistant voltage-sensitive Ca2+ influx pathways. Combined incubations with nifedipine 10 microM and 8-Br-cGMP reduced KCl-evoked intracellular Ca2+ concentration to a greater extent that each compound separately. Moreover, 8-Br-cGMP failed to affect the [Ca2+]i transient induced by the L-type Ca2+ channel agonist Bay K 8644 (1 microM) under conditions of low depolarization. Neomycin (0.2 mM) and omega-AgaToxin-IVA (AgTx) (1 microM) inhibited the calcium transient to a similar extent, and this inhibition was not enhanced by the presence of 8-Br-cGMP. It is concluded that 8-Br-cGMP modulated the dihydropyridine-insensitive Ca2+ influx pathway in the chromaffin cell.
Rodriguez-Pascual
F
F
Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.
Miras-Portugal
M T
MT
Torres
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D004095:Dihydropyridines / Q000494:pharmacology; D009355:Neomycin / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000187:drug effects* / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D015290:Second Messenger Systems; D013111:Spider Venoms / Q000494:pharmacology; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA
D015220:Calcium Channels; D004095:Dihydropyridines; D009419:Nerve Tissue Proteins; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; C016276:8-bromocyclic GMP; D003994:Bucladesine; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine; D020866:omega-Conotoxin GVIA; D006152:Cyclic GMP; D009355:Neomycin; D002118:Calcium