title: Effects of aminoglycoside antibiotics on bound calcium and contraction in guinea-pig atria.
abstract: We studied the effect of three aminoglycoside antibiotics which have been shown to replace Ca from lipid monolayers on the superficially bound Ca of isolated beating left atria from guinea-pigs. The cellular Ca content was determined by means of 45Ca after having attained complete exchange. The antibiotics dibekacin, sisomicin, and gentamicin, all reduced the cellular Ca content by 10-20% in a dose-dependent manner. The loss of superficially bound Ca was accompanied by a decline of the contractile force by 40-90%. It is concluded that in isolated atrial muscle it is the amount of Ca bound to the outer surface of the cardiac plasmalemma, rather than the extracellular Ca2+ concentration, that determines contraction height.
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D003864:Depression, Chemical; D003982:Dibekacin / Q000494:pharmacology; D005839:Gentamicins / Q000494:pharmacology; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D012853:Sisomicin / Q000494:pharmacology
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D005839:Gentamicins; D003982:Dibekacin; D002118:Calcium; D012853:Sisomicin