Alpha 1-adrenergic stimulation of phosphatidylinositol turnover and respiration of brown fat cells.
The alpha-adrenergic agonist phenylephrine (in the presence of the beta-adrenergic antagonist alprenolol) stimulated respiration and incorporation of [3H]glycerol and [32P] Pi into phosphatidylinositol of hamster brown fat cells in a concentration-dependent manner. Both responses were preferentially inhibited by prazosin as compared with yohimbine, indicating alpha 1 specificity. Uniquely, prazosin inhibition of phenylephrine-stimulated phosphatidylinositol metabolism had two components, since 30% of the response was inhibited by less than 1 nM prazosin, 10 nM gave no further inhibition, and 100 nM prazosin completely inhibited the response. The phosphatidylinositol response was still present in Ca2+-free buffer, although reduced in magnitude. The concentration relationships of the effects of agonists and antagonists were compared with those of previous results of [3H]prazosin binding and with phenylephrine potency to compete for binding. On the basis of these comparisons, it is suggested that the highly prazosin-sensitive part of the phosphatidylinositol response may be closely associated with receptor occupation.
D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism*; D000526:Alprenolol / Q000494:pharmacology*; D000818:Animals; D006224:Cricetinae; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008647:Mesocricetus; D010101:Oxygen Consumption / Q000187:drug effects; D010656:Phenylephrine / Q000494:pharmacology*; D010710:Phosphates / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis; D010716:Phosphatidylinositols / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011224:Prazosin / Q000494:pharmacology; D014316:Tritium; D015016:Yohimbine / Q000494:pharmacology
D010710:Phosphates; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D014316:Tritium; D010656:Phenylephrine; D015016:Yohimbine; D000526:Alprenolol; D005990:Glycerol; D011224:Prazosin