Exercise activation of myocardial lipoprotein lipase in male and estrogen-treated female rats.
Lipoprotein lipase (LPL) is the rate-limiting enzyme in the utilization of plasma triglycerides by extrahepatic tissues. The present study examined the effect of estrogen upon the circadian rhythm of rat myocardial LPL and upon the endothelial-bound and tissue components of rat myocardial LPL immediately after exhaustive exercise. Female rats were ovariectomized at 28 days. Estrogen replaced female rats (ER) received 17-beta-estradiol in sunflower oil (200 micrograms/100 g body weight/week for 4 weeks). Oil-injected female rats (OI) received sunflower oil (0.1 mL/100 g body weight/week for 4 weeks). Normal male rats (M) were studied for comparison. ER, OI, and M animals were killed every four hours starting at 8 AM. Estrogen treatment did not alter the circadian rhythm of LPL activity. A second group of animals were run to exhaustion on a motorized treadmill, starting at 9 AM. ER animals performed significantly more work (P less than 0.05) than OI or M rats. Liver glycogen concentration was reduced 96.8% to 97.8% from control in all three groups after exercise. Both the tissue and endothelial fractions of LPL activity were elevated after exercise in all three groups. Exercised ER females (116.3 +/- 9.0 units) had significantly higher cardiac tissue enzyme activity than exercised males (85.0 +/- 9.4 units). Heparin-releasable LPL activity in exercised ER rats (65.3 +/- 5.7 units) was 43% higher than in exercised M rats (45.5 +/- 5.6 units) and 53% higher than in OI female rats (42.6 +/- 8.1 units).(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects; D004789:Enzyme Activation; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010477:Perfusion; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000201:enzymology
D004967:Estrogens; D008071:Lipoprotein Lipase