Hepatic capillary pressure is estimated using triple vascular
occlusion method in isolated canine liver.
Shibamoto, Toshishige, Hong-Gang Wang, Satoshi Tanaka, and Shozo
Koyama.
Department of Physiology, Division 2, Shinshu University School of
Medicine, Matsumoto 390, Japan
APStracts 3:0178R, 1996.
We determined whether the triple vascular occlusion pressure (Pto),
the equilibration pressure obtained when the hepatic artery, portal
and hepatic veins were occluded simultaneously, represented the
capillary pressure (Pc) in isolated bivascularly blood-perfused
canine livers. Effects of a bolus injection of histamine
(0.160[mu]g), norepinephrine (NE, 1600[mu]g), or acetylcholine (ACh,
0.0110[mu]g) into the portal vein or the hepatic artery were also
studied on vascular resistance distribution using Pto as a measure of
Pc. The livers were perfused at constant flow via portal vein and at
constant pressure via hepatic artery. Pto was compared with Pc
measured using the traditional gravimetric method (Pc,i). Pto and
Pc,i showed a strong correlation (Pto= -0.02+0.98 Pc,i; r=0.83,
p=0.0018). With comparisons, the intercept was not significantly
different from zero and the slope was not different from 1.00,
indicating that Pto accurately represented Pc. The resting
postsinusoidal vascular resistance comprised of 54% of the total
hepatic vascular resistance (Rt). Portal or arterial injection of
histamine increased predominantly hepatic venous resistance (Rhv)
over portal resistance with liver weight gain. NE constricted both
portal vein and hepatic artery in greater magnitude than hepatic
vein, as evidenced by a significant decrease in the Rhv/Rt ratio.
This precapillary constriction was accompanied by a significant
decrease in liver weight. In contrast, ACh contracted both portal and
hepatic veins similarly without liver weight change. We conclude that
Pto is an excellent estimate of the capillary pressure in isolated
blood-perfused canine livers and that the hepatic vascular resistance
sites in the resting states are located evenly in the pre- and
postsinusoidal vessels. Intraportal or intraarterial infusion of
histamine, norepinephrine and acetylcholine produced
characteristically different changes in hepatic vascular resistances
and hepatic volume. Pto could be applied in experimental research on
hepatic hemodynamics.
Received 10 September 1995; accepted in final form 29 April 1996.
APS Manuscript Number R559-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 May 96