title: The effect of amiloride and its analog dichlorobenzamil on the cardiac chronotropic responses of myocardial cell aggregates in culture to alterations of extracellular potassium or calcium.
abstract: 1. Cardiac ventricular myocytes aggregates from 7-day-old chick embryos show a decrease in beating rate with increasing [K+]0, from 1 to 10 mM, and stop beating at 10 mM. 2. Amiloride, at 10(-7) and 10(-6) M, produced a significant (P less than 0.05) accentuation of the effects of increasing [K]0 that were dose dependent and produced an earlier cessation of spontaneous beating. 3. The amiloride analogue 3',4'-dichlorobenzamil (DCB), that preferentially inhibits Na+/Ca2+ exchange, produced a significant (P less than 0.05) accentuation of the effects of [K+]0 that were greater than that produced by amiloride. 4. When [Ca]0 was increased from 2.2 to 5.0 mM, cardiac beating rate increased, became irregular and then stopped at [Ca2+]0 of 5 mM. 5. DCB, but not amiloride, significantly (P less than 0.05) accentuated the changes with increasing [Ca2+]0. Thus inhibition of Na+-Ca2+ exchange accentuates the effect of increased [Ca]0 on the heart.
authors.affiliation: Cardiovascular Research Laboratories, University of British Columbia, Vancouver, Canada.
authors.forename: S W
authors.initials: SW
authors.lastname: Rabkin
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002449:Cell Aggregation / Q000187:drug effects*; D002478:Cells, Cultured; D002642:Chick Embryo; D006339:Heart Rate / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*
chemical_list: C041470:3',4'-dichlorobenzamil; D000584:Amiloride; D011188:Potassium; D002118:Calcium