Hepatic galactose elimination kinetics in the intact pig

Abstract

The hepatic galactose elimination kinetics was studied in eight anaesthetized pigs by hepatic vein catheterization. Galactose was given as successive constant intravenous infusions so that steady-state concentrations, ranging from 50 μmol/l to 8 mmol/l, were obtained. Concentrations were measured in a peripheral artery and in the hepatic veins. Hepatic blood flow was determined by constant infusion of indocyanine green. The elimination kinetics is described by a mathematical model which assumes that the liver sinusoids are perfused with unidirectional blood flow and that the elimination in the hepatocytes takes place according to Michaelis-Menten kinetics. This creates a decreasing sinusoidal blood concentration from the inlet to the outlet of the liver. The estimated maximal elimination rate, V_max, was on average 0.67 mmol min^-1 kg^-1 liver (range 0.55–0.95) and the half saturation concentration K_m 0.25 mmol/l (0.12–0.58). The estimate of K_m is similar to the value found in the isolated perfused pig liver (0.23 mmol/l), whereas the estimate of V_max is about 50% higher (0.43 mmol min^-1 kg^-1 liver), probably due to both extrahepatic elimination in the splanchnic area and a better function of the liver in situ than in the isolated preparation.

Key-words:

• enzyme kinetics
• liver circulation
• liver metabolism