Characterization of the alpha 1-adrenoceptors of rat white fat cells.

Activation of alpha 1-adrenoceptors stimulates the labeling of phosphatidylinositol in rat fat cells. The potency order of agonists was: epinephrine greater than norepinephrine greater than methoxamine; phenylephrine was a partial agonist for this effect. The action of norepinephrine was blocked by alpha-adrenergic antagonists in the following order of potency: prazosin greater than phentolamine greater than phenoxybenzamine greater than yohimbine. Trypsinization of fat cells nearly abolished the effect of norepinephrine indicating that alpha 1-adrenoceptor activation occurs at the outer surface of the plasma membrane.