CARDIAC HEPARIN-RELEASABLE LIPOPROTEIN-LIPASE ACTIVITY IN FRUCTOSE-HYPERTENSIVE RATS - EFFECT OF CORONARY VASODILATION

Lipoprotein lipase (LPL) is an endothelium-bound enzyme that is rate d etermining for the clearance of triacylglycerol-rich lipoproteins. We assessed cardiac heparin-releasable LPL activity in an acquired model of hypertension, the fructose-hypertensive rat. Fructose feeding (10% solution in drinking water ad libitum) for 2 (short-term) or 4-6 (long term) weeks induced hypertension, hypertriglyceridemia, and hyperinsul inemia in male Wistar rats. After short-and long-term fructose treatme nt, LPL activity in coronary perfusates was determined by retrogradely perfusing the hearts with heparin. Short-term fructose treatment did not alter cardiac heparin-releasable LPL activity, whereas a significa nt decrease in LPL activity was seen in the long-term treated group. D iscontinuation of fructose treatment for 2 weeks from the long-term gr oup normalized blood pressure and cardiac heparin-releasable LPL activ ity. Interestingly, acute vasodilation by in vitro perfusion of corona ry vasodilators like nifedipine and CGS-21680 increased cardiac hepari n-releasable LPL activity in the long-term group to control levels. Th ese studies demonstrate that long-term fructose-induced hypertension m ay play a significant role in regulating cardiac LPL activity. Whether or not this altered LPL activity has a role in the regulation of fatt y acid supply to the hypertensive heart has vet to be determined.