CARDIAC LIPOPROTEIN-LIPASE IN THE SPONTANEOUSLY HYPERTENSIVE RAT

Objective: The objectives of the present study were to determine funct ional (i.e., heparin-releasable) and intracellular (i.e., heparin-non- releasable) cardiac lipoprotein lipase (LPL) activity during the devel opment of hypertension in spontaneously hypertensive (SHR) rats. Metho ds: Male WKY and SHR rats were killed before (7-8 weeks of age) and fo llowing (15-16 weeks of age) the development of severe hypertension in SHR rats. LPL activity in coronary perfusates was determined by retro gradely perfusing the hearts with heparin (5 U/ml). Cardiac myocytes w ere also isolated from the two groups of rats by collagenase digestion , and surface-bound and intracellular LPL activity measured. Results: With the development of hypertension in SHR rats, there was a concomit ant and progressive reduction in the heparin-releasable coronary endot helial LPL activity. Neither insulin action nor cell-associated enzyme activity could explain this low LPL activity in coronary blood vessel s. However, acute vasodilation with nifedipine (a Ca2+ influx blocker) or CGS-21680 (A(2)-purinergic receptor agonist) increased the peak he parin-releasable LPL activity in hearts isolated from SHR rats. Conclu sions: Our results indicate that hypertension per se may play a signif icant role in regulating cardiac LPL activity, and hence fatty acid su pply to the hypertensive SHR rat heart.