Hepatic capillary pressure is estimated using triple vascular occlusion method in isolated canine liver

Abstract

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 (0.1-60 micrograms), norepinephrine (NE; 1-600 micrograms), or acetylcholine (ACh; 0.01-10 micrograms) 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 the portal vein and at constant pressure via the 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 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 the portal vein and the hepatic artery in greater magnitude than the 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 Pc 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 intra-arterial infusion of histamine, NE, and ACh produced characteristically different changes in hepatic vascular resistances and hepatic volume. The Pto technique could be applied in experimental research on hepatic hemodynamics.

Effects of Hct and norepinephrine on segmental vascular resistance distribution in isolated perfused rat livers

“…In the liver, little is known about the effect of changes in blood Hct on the longitudinal distribution of vascular resistance. Thus we examined the effect of different Hct on the longitudinal vascular resistance distribution in the rat liver.Norepinephrine constricts predominantly the presinusoidal vessels over the postsinusoidal vessels of hepatic veins (3,15,22,24). Maass-Moreno and Rothe (15), by using the doublelumen catheter inserted through the caval wall into hepatic vein in anesthetized dogs, reported that an infusion of norepinephrine caused a large increase in portal venous pressure but little change in pressure gradient from the large hepatic vein to vena cava.…”

“…The responsiveness of the hepatic longitudinal vascular segments differs depending on vasoactive agents (3,23,24). The differences in the response of these vascular segments to a variety of stimuli are, in part, due to the intrinsic vasomotor properties of the blood vessels as well as their passive viscoelastic properties.…”

Effects of Norepinephrine and Histamine on Vascular Resistance in Isolated Perfused Mouse Liver

“…In rat livers, histamine did not contract or dilate hepatic vessels [11]. On the other hand, norepinephrine predominantly contracts the presinusoidal veins over the postsinusoidal veins in dogs, rabbits, rats, and guinea pigs [4,7,9,11]. However, the effects of these vasoconstrictors have not been determined on hepatic vascular resistance distribution in mice.…”

“…predominantly contracts the postsinusoidal veins with resultant hepatic congestion in dogs [9,10] and guinea pigs [11], but this substance constricts presinusoidal vessels in rabbits [4]. In rat livers, histamine did not contract or dilate hepatic vessels [11].…”

“…By using the vascular occlusion methods for measurement of the hepatic sinusoidal pressure [2, 9], we have recently shown that the hepatic longitudinal vascular responsiveness to vasoactive substances differs among different species, such as dogs, rabbits, rats, and guinea pigs [4][5][6][9][10][11]. Histamine termine the presinusoidal (R pre ) and postsinusoidal (R post ) resistances.…”