AJP - Gastrointestinal and Liver Physiology, Vol 255, Issue 2 194-G200, Copyright © 1988 by American Physiological Society
Continuous monitoring of portal vein and hepatic artery hemodynamics in unrestrained rats
A. Braillon and M. J. Brody
Department of Pharmacology, College of Medicine, University of Iowa, Iowa City 52242.
Continuous measurement of portal vein and hepatic artery blood flows during
physiological experimental conditions, even in large animals, poses
difficult problems. We report the successful use of miniaturized flow
probes and pulsed Doppler flowmetry for chronic monitoring of hepatic
artery and portal vein flows in intact unrestrained rats and describe the
probe construction and implantation. Proportionality between portal vein
velocity and portal flow was made possible by a technique for stabilizing
the diameter of the venous segment from which velocity is recorded. The
accuracy of the method in detecting changes in portal vein flow was
established by the high statistically significant correlation between
changes in velocity recorded simultaneously from portal vein and superior
mesenteric artery in a series of rats with ligated celiac and inferior
mesenteric arteries. In these preparations all portal vein flow is derived
from the superior mesenteric artery. Complex dynamic changes in the hepatic
circulation of conscious unrestrained rats were recorded in response to
systemic injections of glucagon and angiotensin II. In the resting state
several characteristic velocity patterns were recorded from the portal
vein. Oscillations linked to respiration were not observed while the
animals rested quietly but were noted during sleep and anesthesia. Two
hitherto unrecognized patterns produced respectively by the pulsations of
the superior mesenteric artery and by spontaneous contractions of the
portal vein were also observed. The method described here provides the
first opportunity to study hepatic circulation in chronically instrumented
rats during physiological experimental conditions.
