Importance of flow and haematocrit for metabolic function of perfused rat liver

The influence of flow rate and haematocrit on the metabolic function of once-through perfused rat liver, as assessed by galactose elimination and oxygen uptake, was studied. Rats weighting from 195 to 220 g were used. Each of eleven experiments consisted of four periods; the blood flow rate was 10 ml/min in the first and the last period, and it was varied at random from 0.6 to 18 ml/min in the second and the third period. Haematocrit values of either 0.40, 0.28 or 0.16 1/1 were constant in each experiment. The input concentration of galactose was 1.7 mmol/l. Both galactose elimination and oxygen uptake were independent of the flow rate between 6 and 18 ml/min. At flow rates below 6 ml/min (i.e. below 0.9 ml/min/g liver) both functions were reversibly decreased in parallel with the flow. The values were highly correlated. There was a trend towards a lower galactose elimination rate and oxygen uptake at lower haematocrit values. It is emphasized that flow rate and haematocrit must be kept above certain limits in metabolic studies with perfused rat liver.