Effects of estradiol-17 beta on the net hepatic extraction of triglyceride in vivo in fed and fasted sheep.
The effects of estrogen and fasting on hepatic metabolism were studied by an arteriovenous difference technique in six multicatheterized ewes. In each experiment samples were collected during fed and 3- and 5-day fasted states before, and 10 to 17 days after the animals had been implanted with 550 mg of estradiol-17 beta. The implants elevated plasma estradiol five- to seven-fold. Plasma concentrations of insulin and triglyceride (TG) were increased (P less than 0.01) by 131% and 62% respectively by estradiol in fed sheep. Concurrent circulating concentrations of glucose, glycerol, free fatty acids, and beta-hydroxybutyrate were unaffected. During fasting estradiol elevated circulating concentrations of beta-hydroxybutyrate slightly, while levels of other metabolites and insulin were not different from fasted controls. In fed animals estradiol had no effect on the net hepatic uptake (NHU) of TG or glycerol but during fasting estradiol reduced the NHU of TG and glycerol by 47% and 31% (P less than 0.01) respectively. In addition, estradiol reduced the net hepatic production of beta-hydroxybutyrate in fed, but not in fasted animals. Net hepatic exchanges of glucose, or FFA were not affected by estradiol in either the fed or fasted state. Fasting increased the NHU of TG (P less than 0.05) and glycerol (P less than 0.01). The results of this study suggest that estradiol, at physiological concentrations, has lipotropic and anti-ketogenic effects on the ruminant liver. However, the anti-ketogenic effect is not apparent in fasted animals. Secondly, it appears that the hepatic lipidosis which often occurs in ruminants during negative energy balance is due largely to an increase in the NHU of circulating TG.
Kerr
D E
DE
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada.
Chaplin
R K
RK
Laarveld
B
B
D000818:Animals; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D005215:Fasting; D005260:Female; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
D014280:Triglycerides; D004958:Estradiol