beta 2-Adrenoceptors in rat liver microcirculation.
1. Rat liver sinusoids were observed by a microscopic in vivo transillumination method. The diameter of liver sinusoids and intrasinusoid erythrocyte flow velocities were measured quantitatively by a close-circuit television technique. 2. Both isoprenaline and the selective beta 2-adrenoceptor agonist terbutaline produced a concentration-dependent dilatation of liver sinusoids and slowed erythrocyte flow velocity. The effects of isoprenaline and terbutaline were antagonized by propranolol but not by the selective beta 1-adrenoceptor antagonist atenolol. Propranolol alone produced constriction of the liver sinusoids and increased erythrocyte flow velocity; these effects were not produced by atenolol. 3. The percentage dilatations produced by isoprenaline alone, isoprenaline in the presence of phenoxybenzamine and isoprenaline in the presence of phenylephrine-induced constriction were similar. 4. It is proposed that the beta-adrenoceptors in liver sinusoids are of the beta 2-type, and their physiological role was to counteract constrictor responses produced by alpha-adrenoceptor activity.
D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008102:Liver Circulation / Q000187:drug effects*; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D010643:Phenoxybenzamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013726:Terbutaline / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D010643:Phenoxybenzamine; D010656:Phenylephrine; D001262:Atenolol; D007545:Isoproterenol; D013726:Terbutaline