Ca2+ channels in chick neural retina cells characterized by 1,4-dihydropyridine antagonists and activators.
The voltage-sensitive calcium channel in cultured chick neural retina cells was characterized by the actions of the enantiomers of Bay K 8644 and 202-791 and other 1,4-dihydropyridines. These cells showed time- and voltage-dependent Ca2+ uptake that was stimulated by K+ depolarization and blocked by the inorganic calcium channel blockers Cd2+ and Co2+. A small fraction only (15% maximum) of the uptake was inactivated by predepolarization of the cells with 80 mM K+. Ca2+ uptake was sensitive to the 1,4-dihydropyridine calcium channel antagonists and activators. (S)-Bay K 8644 and (S)-202-791 stimulated the Ca2+ uptake, and (R)-Bay K 8644 and (R)-202-791 as well as nitrendipine and PN 200-110 inhibited Ca2+ uptake stimulated by K+ depolarization or channel activators. The K+ depolarization-stimulated uptake was inhibited by 90%, but the activator-stimulated uptake was completely blocked by the 1,4-dihydropyridine antagonists. The potencies of these agents as inhibitors of Ca2+ uptake were significantly lower than the binding affinities in membrane preparations from the same cells or their binding and pharmacologic affinities in vascular smooth muscle. K+ depolarization or (S)-Bay K 8644 induced 45Ca2+ uptake was not observed in a glial cell culture. [3H]Nitrendipine and [3H]PN 200-110 bound to membrane preparations of the cells consistent with the presence of a single type of high affinity binding site.(ABSTRACT TRUNCATED AT 250 WORDS)
Wei
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Department of Biochemical Pharmacology, School of Pharmacy, State University of New York, Buffalo 14260.
Rutledge
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A
Zhong
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Ferrante
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Triggle
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DJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002478:Cells, Cultured; D002642:Chick Embryo; D004095:Dihydropyridines / Q000494:pharmacology*; D017275:Isradipine; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D010069:Oxadiazoles / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D012160:Retina / Q000166:cytology / Q000378:metabolism*; D013237:Stereoisomerism
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002132:Calcium Radioisotopes; D004095:Dihydropyridines; D009467:Neuromuscular Depolarizing Agents; D010069:Oxadiazoles; D011188:Potassium; D002118:Calcium; D017275:Isradipine