Cardiac lipoprotein lipase in the spontaneously hypertensive rat.
OBJECTIVE
The objectives of the present study were to determine functional (i.e., heparin-releasable) and intracellular (i.e., heparin-non-releasable) cardiac lipoprotein lipase (LPL) activity during the development of hypertension in spontaneously hypertensive (SHR) rats.


METHODS
Male WKY and SHR rats were killed before (7-8 weeks of age) and following (15-16 weeks of age) the development of severe hypertension in SHR rats. LPL activity in coronary perfusates was determined by retrogradely perfusing the hearts with heparin (5 U/ml). Cardiac myocytes were 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 concomitant and progressive reduction in the heparin-releasable coronary endothelial LPL activity. Neither insulin action nor cell-associated enzyme activity could explain this low LPL activity in coronary blood vessels. However, acute vasodilation with nifedipine (a Ca2+ influx blocker) or CGS-21680 (A2-purinergic receptor agonist) increased the peak heparin-releasable LPL activity in hearts isolated from SHR rats.


CONCLUSIONS
Our results indicate that hypertension per se may play a significant role in regulating cardiac LPL activity, and hence fatty acid supply to the hypertensive SHR rat heart.
Sambandam
N
N
Division of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
Chen
X
X
Cam
M C
MC
Rodrigues
B
B
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D006973:Hypertension / Q000201:enzymology*; D007424:Intracellular Fluid / Q000201:enzymology*; D008071:Lipoprotein Lipase / Q000032:analysis / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D009543:Nifedipine / Q000494:pharmacology; D010477:Perfusion; D010627:Phenethylamines / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014665:Vasodilator Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D014665:Vasodilator Agents; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D006493:Heparin; D008071:Lipoprotein Lipase; D009543:Nifedipine; D000241:Adenosine