Beta-Adrenergic receptors in rat fat cells and their relationship with lipolysis.
Norepinephrine stimulated lipolysis in rat fat cells while (-)-alprenolol completely inhibited this lipolysis. (-)-Alprenolol competed for (-)-[3H] dihydroalprenolol (DHA) binding sites on rat fat cells. The specific (-)-[3H]DHA binding sites identified by competition with (-)-alprenolol were found to be transferred to the solubilized supernatant during preparation of endogenous lipid droplets from the fat cells. Although the lipid droplets did not exhibit specific (-)-[3H]DHA binding, norepinephrine induced lipolysis in a cell-free system consisting of the lipid droplets and hormone-sensitive lipase (HSL). Norepinephrine-induced lipolysis in the cell-free system was inhibited by propranolol and (-)-alprenolol, but not by phenoxybenzamine. The lipolytic action of norepinephrine and the anti-lipolytic actions of propranolol and (-)-alprenolol disappeared after sonication of the lipid droplets in the cell-free system. These results suggest that the adrenergic receptor concerned with lipolysis in fat cells may not be a specific (-)-[3H]DHA binding site, but may be closely related to the lipid droplets.
Okuda
H
H
2nd Department of Medical Biochemistry, School of Medicine, Ehime University.
Morimoto
C
C
Tsujita
T
T
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018663:Adrenergic Agents / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000526:Alprenolol / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D004082:Dihydroalprenolol / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013010:Sonication
D018663:Adrenergic Agents; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000526:Alprenolol; D011433:Propranolol; D009638:Norepinephrine