title: Direct myocardial depressant effects of gentamicin.
abstract: Effects of gentamicin on myocardial contractile performance were examined in isolated, electrically driven, rat left atria. This aminoglycoside antibiotic produced a maintained and concentration-dependent (0.0156-0.25 mM) depression of myocardial contractile tension that was reversible by replacing the incubation media with gentamicin-free solution. Time to peak tension and total contraction time were not discernibly altered by gentamicin. The negative inotropic response elicited by gentamicin was antagonized in a competivitive-like manner by increasing the calcium ion (Ca2+) concentration of the bathing solution, whereas, the depressant effects of gentamicin were antagonized by norepinephrine in a non-competitive-like manner. Present findings demonstrate a direct negative inotropic effect of gentamicin and suggest that this antibiotic interferes with the participation of Ca2+ in the events leading to mecahnical activity of atrial myocardium.
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004558:Electric Stimulation; D005839:Gentamicins / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006325:Heart Atria / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats
chemical_list: D000889:Anti-Arrhythmia Agents; D005839:Gentamicins; D002118:Calcium; D009638:Norepinephrine