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  • Title: Inhibition by 5-N-(4-chlorobenzyl)-2',4'-dimethylbenzamil of Na+/Ca2+ exchange and L-type Ca2+ channels in isolated cardiomyocytes.
    Author: Sharikabad MN, Cragoe EJ, Brørs O.
    Journal: Pharmacol Toxicol; 1997 Feb; 80(2):57-61. PubMed ID: 9060035.
    Abstract:
    The inhibitory effect of the amiloride derivative 5-N-(4-chlorobenzyl)-2',4'-dimethylbenzamil (CBDMB) on calcium (Ca2+) uptake via sarcolemmal sodium-calcium (Na+/Ca2+) exchange and L-type Ca2+ channels was investigated in isolated adult rat ventricular cardiomyocytes under depolarizing conditions in cells preincubated with 1 mM ouabain or 137 mM lithium (Li+), respectively. Fifteen or 120 min. preincubation with CBDMB inhibited Ca2+ uptake via Na+/ Ca2+ exchange in Na(+)-loaded depolarized cells completely at 100 microM with an IC50 of 21 microM. After 120 min. preincubation, CBDMB inhibited Ca2+ uptake via L-type Ca2+ channels by 75.1 +/- 8.1% (mean and S.E.M.) and IC50 of 4 microM, whereas no significant inhibition was observed after 15 min. preincubation. (+)-Isradipine (10 microM) inhibited high potassium (K+) induced Ca2+ uptake via L-type Ca2+ channels by 35% after 15 min. and by 70% after 120 min. preincubation. Inhibition by CBDMB of specific (+)-[3H]isradipine binding to L-type Ca2+ channels showed similar concentration dependency as inhibition of Ca2+ uptake via L-type Ca2+ channels. In conclusion, CBDMB inhibits sarcolemmal Na+/Ca2+ exchange in rat ventricular cardiomyocytes rapidly. However, after longer preincubation periods, L-type Ca2+ channels are inhibited as well and with higher potency than Na+/Ca2+ exchange.
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