Beta-adrenergic receptors in white fat cells of cold-acclimated rats.
Beta-adrenergic receptors were studied in membranes prepared from isolated fat cells obtained from both control and cold-acclimated rats. Beta-adrenergic receptors were identified using beta-adrenergic antagonist, (-) - [3H] dihydroalprenolol. Scatchard plots of specific binding suggest the existence of two binding sites for (-) - [3H] dihydroalprenolol with different affinities. Beta-adrenergic agonists competed for specific binding sites with typical beta 1-adrenergic specificity. There appears to be approximately 5,000 sites of high affinity per fat cell. Cold-acclimation (4 weeks at 4 degrees C) reduced adipocyte size; it did not appear to alter either the maximal number of binding sites of high and low affinity, or their affinity for beta-antagonists or agonists; however the density of binding sites in the fat cell was increased in cold-acclimated rats. It is concluded that the cold-adaptative process which induces in vivo the enhancement of calorigenic effect of norepinephrine is not found at the level of beta-receptors in white fat cells. The increased lipolytic response to norepinephrine observed in vitro in epididymal fat may be explained by cold-induced modifications in cell size and number.
D000064:Acclimatization; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D003080:Cold Temperature; D004082:Dihydroalprenolol; D007700:Kinetics; D008297:Male; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D014280:Triglycerides; D004082:Dihydroalprenolol