Metabolic effects of beta, alpha 1, and alpha 2 adrenoceptor activation on brown adipocytes isolated from the perirenal adipose tissue of fetal lambs.

Brown adipocytes can be readily isolated by collagenase digestion of perirenal adipose tissue from fetal lambs. In isolated cells the addition of phenylephrine in the presence of alprenolol (to specifically stimulate alpha adrenoceptors) resulted in an increase in de novo synthesis of phosphatidylinositol and phosphatidic acid. The stimulatory effects were preferentially inhibited by prazosin while yohimbine had little effect, indicating that the adrenoceptors were alpha 1 in character. Isoproterenol stimulated cyclic adenosine monophosphate (AMP) accumulation and lipolysis as well as respiration. Forskolin also mimicked the effects of beta adrenergic stimulation. Clonidine, a specific alpha 2 adrenergic agonist, inhibited lipolysis and cyclic AMP accumulation. Insulin inhibited cyclic AMP accumulation and stimulated glucose metabolism in the adipocytes. The present studies indicate that beta, alpha 1, and alpha 2 adrenergic as well as insulin responses can be detected in ovine perirenal adipocytes.