PMID: 8595623Nov 1, 1995Paper

Pharmacology of the high-affinity apamin receptor in rabbit heart

Cardiovascular Research
J A Schetz, P A Anderson

Abstract

Apamin is a potent blocker of calcium-activated small conductance potassium (SK) channels in neurons, liver, skeletal muscle and ileum smooth muscle, but not in cardiac muscle. Cardiac muscle is devoid of SK channels; however, in isolated, single ventricular myocytes apamin is an extremely potent blocker of the L-type calcium current, and the anti-arrhythmic drug quinidine reverses apamin block. To characterize the receptor binding properties and pharmacology of the apamin receptor in heart. The binding properties of the apamin receptor were determined by rapid filtration of purified rabbit heart membranes. Monoiodinated apamin binds to a labile, membrane-bound protein in heart membranes at a single, high-affinity site (KD = 8.07 +/- 2.14 pM and Bmax = 686 +/- 167 fmoles/mg protein, significant run test at P = 0.05 for a one site fit). 125I-apamin binding is dose-dependently inhibited by apamin, scyllatoxin, quinidine, amiloride, as well as a variety of di- and trivalent cations that are classical blockers of L-type calcium channels (e.g. Co2+, Cd2+, Mn2+, La3+, Gd3+). The cardiac apamin receptor is also critically dependent upon pH, temperature and KCl, and co-purifies in the same membrane fraction as L-type cardiac Ca2+ chann...Continue Reading

Citations

Dec 5, 2006·The Journal of Biological Chemistry·Andreas NoltingMartin Stocker
Jun 23, 2004·Toxicon : Official Journal of the International Society on Toxinology·Chen-Qi XuCheng-Wu Chi

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