Lipid accumulation in the perfused rat heart after isoproterenol administration

Isoproterenol is a potent lipolytic agent. It has also been shown to induce accumulation of lipid droplets in the myocardium in vivo. The isolated working rat heart model was applied to evaluate the effect in vitro. Twenty-four rats were randomly separated into four experimental groups of six rats, all receiving Krebs-Hensleit buffer with 11mM glucose. The control group had no supplement, the other groups received either 10(-5) M isoproterenol, 1.2 mM palmitate, or a combination of the two. Tissue levels of triglycerides and phospholipids, and the fractional volume of lipid droplets were determined at the end of the 30 min perfusion in the working heart mode. Ventricular function was monitored continuously and showed a marked increase in the isoproterenol treated groups. The level of tissue phospholipids remained unchanged in all groups. Whereas tissue triglycerides were significantly increased in the group receiving only palmitate as compared to the other groups. A corresponding increase was, however, not found to be significant for lipid droplet quantitation. The results are discussed in terms of possible mechanisms for isoproterenol-induced accumulation of neutral lipids in the myocardium.