Effect of fatty acid composition of rat heart myocytes on their electrical activity

Rat heart myocytes were cultured for up to 16 days in medium containing 20% non-delipidated fetal calf and horse serum (control cells) and in medium containing lipid depleted serum supplemented with either palmitic or linoleic acid. The main change in fatty acid composition of cellular lipids consisted of an increase in the ratio of linoleic to oleic acid from 0.15 in palmitate supplemented cells and 0.64 in control cells to 2.6 in linoleate supplemented cells. Cells grown in the presence of linoleic acid showed enhanced repolarization compared to those grown with palmitic acid or to control cells. The maximal dV dt during repolarization was 0.678 ± 0.113 V/s for cells grown with linoleic acid; 0.405 ± 0.105 V/s for cells grown with palmitic acid and 0.397 ± 0.007 V/s for the control cells. The duration of action potential and the value of dV dt, when compared at similar degrees of repolarization, showed significantly enhanced repolarization during the initial phase in cells grown with linoleic acid. Maximal diastolic membrane potential and the depolarization phase were similar in cells cultured with linoleic or palmitic acid. We explain these results by the hypothesis that the enrichment in linoleic acid of membrane lipids causes a rise in the flux of Cl^- and K⁺ through their respective channels leading to an augmented initial phase of repolarization.