Different contributions of L- and Q-type Ca2+ channels to Ca2+ signals and secretion in chromaffin cell subtypes.
In this study, we investigated the contribution of different subtypes of voltage-dependent Ca2+ channels to changes in cytosolic free Ca2+ ([Ca2+]i) and secretion in noradrenergic and adrenergic bovine chromaffin cells. In single immunocytochemically identified chromaffin cells, [Ca2+]i increased transiently during high K+ depolarization. Furnidipine and BAY K 8644, L-type Ca2+ channel blocker and activator, respectively, affected the [Ca2+]i rise more in noradrenergic than in adrenergic cells. In contrast, the Q-type Ca2+ channel blocker omega-conotoxin MVIIC inhibited the [Ca2+]i rise more in adrenergic cells. omega-Agatoxin IVA (30 nM), which blocks P-type Ca2+ channels, had little effect on the [Ca2+]i signal. The N-type Ca2+ channel blocker omega-conotoxin GVIA similarly inhibited the [Ca2+]i rise in both cell types. The effects of furnidipine, BAY K 8644, and omega-conotoxin MVIIC on K+-evoked norepinephrine and epinephrine release paralleled those effects on [Ca2+]i signals. However, omega-conotoxin GVIA and 30 nM omega-agatoxin IVA did not affect the secretion of either amine. The data suggest that, in the bovine adrenal medulla, the release of epinephrine and norepinephrine are preferentially controlled by Q- and L-type Ca2+ channels, respectively. P- and N-type Ca2+ channels do not seem to control the secretion of either catecholamine.
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Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
Michelena
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Núñez
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García-Sancho
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J
García
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AG
Montiel
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D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002417:Cattle; D002838:Chromaffin System / Q000166:cytology / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004095:Dihydropyridines / Q000494:pharmacology; D004837:Epinephrine / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D009994:Osmolar Concentration; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D015398:Signal Transduction; D020866:omega-Conotoxin GVIA; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D010455:Peptides; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; C038806:1,4-dihydropyridine; D020866:omega-Conotoxin GVIA; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine