AJP - Heart and Circulatory Physiology, Vol 253, Issue 5 1053-H1058, Copyright © 1987 by American Physiological Society
Participation of adrenoceptors in liver blood flow regulation in anesthetized dogs
N. Terada, S. Koyama, J. Horiuchi and T. Takeuchi
Department of Physiology, Yamanashi Medical College, Japan.
We evaluated involvement of adrenergic receptors in the responses of the
hepatic vasculature to reduction either of portal venous flow or hepatic
arterial inflow. Portal vein occlusion caused an increase in hepatic
arterial blood flow (HAF) and decreases in hepatic arterial pressure (HAP)
and hepatic arterial vascular resistance (HAR) in the intact group. After
pretreatment with either yohimbine or prazosin, but not propranolol,
occlusion of the portal vein produced a greater decrease in HAP as compared
with that in the intact group. No significant changes in HAF, HAR, or
hepatic tissue blood flow (HTF) occurred after the treatment. These results
indicate that the compensatory response of the hepatic arterial vasculature
to altered portal blood flow (PVF) is regulated independently of the
intrahepatic adrenergic receptors. Hepatic arterial occlusion caused a
significant decrease in portal venous pressure, PVF, and HTF. Portal venous
vascular resistance (PVR) was reduced slightly, but not significantly.
After pretreatment with either yohimbine or prazosin, but not propranolol,
occlusion of the hepatic artery produced an opposite effect: to increase
PVF and significantly decrease PVR. These results indicate that
intrahepatic alpha-adrenoceptors participate in the regulation of portal
vascular tone to maintain portal vein pressure at a steady level, when
inflow from the hepatic artery is reduced.
