Norepinephrine: a potential modulator of the hepatic transport of taurocholate. a study in the isolated perfused rat liver.

The effects of norepinephrine on portal blood flow hepatic extraction and intrinsic clearance of taurocholate were studied in the isolated perfused rat liver. Livers were perfused at a constant pressure. [14C]Taurocholate was infused continuously at a rate of 0.6 mumol/min. Then, three increasing doses of norepinephrine were added to the perfusate. Norepinephrine induced a significant dose-dependent reduction in portal blood flow. In spite of this reduction, taurocholate extraction did not increase and intrinsic clearance decreased significantly. When portal blood flow was decreased mechanically, intrinsic clearance was, as expected, flow-independent. The effects of norepinephrine on portal blood flow and intrinsic clearance were antagonised by phentolamine but not by propanolol. Norepinephrine decreases independently both portal blood flow and the vectorial transport of taurocholate. These effects are mediated by alpha adrenergic receptors.