L-Carnitine improves mechanical responses of cardiomyocytes and restores Ca 2+ homeostasis during aging.

L-Carnitine (β-hydroxy-γ-trimethylaminobutyric acid, LC) is a crucial molecule for the mitochondrial oxidation of fatty acids. It facilitates the transport of long-chain fatty acids into the mitochondrial matrix. The reduction in LC levels during the aging process has been linked to numerous cardiovascular disorders, including contractility dysfunction, and disrupted intracellular Ca 2+ homeostasis. The aim of this study was to examine the effects of long-term (7 months) LC administration on cardiomyocyte contraction and intracellular Ca 2+ transients ([Ca 2+ ] i ) in aging rats. Male albino Wistar rats were randomly assigned to either the control or LC-treated groups. LC (50 mg/kg body weight/day) was dissolved in distilled water and orally administered for a period of 7 months. The control group received distilled water alone. Subsequently, ventricular single cardiomyocytes were isolated, and the contractility and Ca 2+ transients were recorded in aging (18 months) rats. This study demonstrates, for the first time, a novel inotropic effect of long-term LC treatment on rat ventricular cardiomyocyte contraction. LC increased cardiomyocyte cell shortening and resting sarcomere length. Furthermore, LC supplementation led to a reduction in resting [Ca 2+ ] i level and an increase in the amplitude of [Ca 2+ ] i transients, indicative of enhanced contraction. Consistent with these results, decay time of Ca 2+ transients also decreased significantly in the LC-treated group. The long-term administration of LC may help restore the Ca 2+ homeostasis altered during aging and could be used as a cardioprotective medication in cases where myocyte contractility is diminished.