Studies of gut and hepatic metabolism in conscious rabbits

The present study was designed to develop the techniques for chronic catheterization of the hepatic and portal venous circulation in conscious rabbits and to apply these techniques to a study of hepatic metabolism in this species. Experiments were made after an 18-h fast and for 4 h after the initial feeding. Measurements of arteriovenous differences of substrates were combined with measurements of hepatic and gastrointestinal blood flow. Hepatic glucose production was suppressed by 60% at 1 h and had returned to control levels by 4 h. The hepatic uptake of lactate declined slightly at 1 h and had returned to control level 2 h after the meal. There was a marked and rapid fall in hepatic ketone body output after refeeding. Although amino acid concentrations displayed a transient increase 1 h after the meal, only the arterial concentration of branched-chain amino acids remained significantly elevated for 4 h. The total hepatic uptake of the gluconeogenic amino acids (alanine, serine, threonine) remained constant. Refeeding resulted in a doubling of arterial insulin concentrations at 1 h followed by a progressive decline over the next 3 h. It is concluded that in rabbits fed a mixed meal partial suppression of hepatic glucose output is mainly due to a decline in glycogenolysis rather than a decrease in gluconeogenesis, shortly after refeeding the liver is able to virtually shut off its ketone body production, the major gluconeogenic precursors (lactate, alanine, glycine, serine, and threonine) may contribute to approximately 40% of the glucose release.(ABSTRACT TRUNCATED AT 250 WORDS)