An Investigation of the Reversal of the Hepatic Venous Circulation in the Isolated Perfused Dog Liver

Abstract

Summary. The changes in the drculatoTy pathways were studied in an isolated perfused canine liver, when the venous circulation was reversed. A radioactive isotope dilution technique was employed, in which two radioactive tracers were used simultaneously, to investigate the nature of the hepatic vascular bed under normal and reversed conditions. The results indicate that when the venus circulation is reversed the hepatic arterial blood fills far less of the vascular bed than under normal conditions. This indicates that there may be a low impedance pathway between the hepatic artery and the portal vein, which enables the hepatic arterial blood, under reversed flow conditions, to reach the portal tract without it traversing the normal arterial pathways through the liver.

Pressure‐flow relationships and effects of noradrenaline and isoprenaline on the hepatic arterial and portal venous vascular beds of the dog.

“…Richardson & P. G. Withrington, unpub-lished observations) preparations, it is not dependent on extrinsic innervation, though the involvement of a local reflex remains a possibility. Arterioportal vascular connexions exist (Cliff, 1971;Rappaport & Schneiderman, 1976) and unidirectional arterioportal flow has been observed (Field & Andrews, 1967;Field, 1970;Rappaport & Schneiderman, 1976): this may offer an explanation for the change in portal vascular resistance occasioned by altering the hepatic arterial inflow pressure and volume which would alter the transmission of arterial pressure and flow to the portal bed. An alternative explanation involves the common outlet channel from the two inflow circuits; alterations in the pressure-flow gradients between the hepatic sinusoids and the hepatic veins might cause changes in the calculated vascular resistance of the other circuit.…”

“…There is structural evidence that direct connexions exist between the hepatic arterial and portal venous vascular bed and, indeed, unidirectional arterio-portal blood flow has been observed (Wakim & Mann, 1942;Bloch, 1955;McCuskey, 1966;Cliff, 1976). It has been suggested, on the basis of studies in which the liver was perfused both normally and retrogradely through the hepatic vein, that there is a low impedance pathway between the hepatic artery and portal vein, which enables the hepatic arterial blood to reach the portal venous system directly (Field & Andrews, 1967;Field, 1970). Further functional evidence for arterio-portal interrelationships lies in the observations that occlusion of the hepatic artery leads to a reduction in portal vascular resistance and that occlusion of the hepatic portal venous inflow occasions vasodilatation of the hepatic arterial vascular bed (Hanson & Johnson, 1966;Greenway & Stark, 1971).…”