A system for the study in situ of the pentose phosphate pathway in rabbit liver

A surgical procedure for the isolation of the liver from the systemic circulation of the anaesthetized rabbit is described. The technique allowed the metabolism in situ of intraportally infused substrates to be followed for periods up to 5min, free from the contaminating influences of metabolism by other body tissues. Details of the procedures necessary to achieve the uniform infusion, homogeneous distribution and containment of ¹⁴C-labelled glucose substrates in the liver by haemostasis are described. Changes in pO₂, pCO₂, pH and the concentrations of NADP⁺, NADPH and glucose during each minute interval of the total 5min period of metabolism are given. Reactant ratios of the lactate dehydrogenase system and the adenine nucleotide system have been calculated from the concentrations of the pertinent metabolites for the same period of metabolism. Glucose production by rabbit liver in situ proceeded at the rate of 1.08μmol/min per g wet wt. of liver during the 5min metabolic interval. The presence of the oxidative reactions of the pentose phosphate pathway of glucose metabolism was inferred from the quotient oxidation of [1-¹⁴C]glucose/oxidation of [6-¹⁴C]glucose=1.8.