Receptors for calcium antagonists.
Calcium antagonists have been divided into 3 different subclasses represented by nifedipine, verapamil and diltiazem. These drugs have different pharmacologic effects and are not interchangeable. Previous studies suggested that all calcium antagonists bind to a 170 kd polypeptide (now called the alpha 2 subunit of the voltage-dependent calcium channel). The apparent molecular weight of this polypeptide characteristically decreased from 170 to 140 kd upon disulfide reduction as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Recent studies demonstrated that calcium antagonists bind to a previously unrecognized 165 kd polypeptide (alpha 1 subunit) that does not change its electrophoretic mobility on disulfide reduction. Because of their similar molecular weights, the 2 polypeptides may overlap each other on polyacrylamide gels. The primary structure of both polypeptides clearly shows, however, that they are different from each other and only the alpha 1 subunit has the features expected of an ion channel.
Schwartz
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A
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.
McKenna
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E
Vaghy
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PL
D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D004110:Diltiazem / Q000494:pharmacology; D006801:Humans; D009543:Nifedipine / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011978:Receptors, Nicotinic; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine