The preparation and properties of isolated chicken hepatocytes

Abstract

Chicken hepatic parenchymal cell suspensions, isolated by an optimised collagenase digestion, were used for a study of hepatic glucose metabolism and its control in the chicken. Characterisation of this iri vitro preparation showed the parenchymal cells immediately after isolation to be similar to those of whole liver, both morphologically and metabolically. This similarity suggested that metabolic studies with isolated hepatocytes might confidently be extrapolated to the situation in the intact animal. However the preparation quality was dependent on collagenase contaminants and all preparations exhibited decreased viability throughout subsequent incubations.

Glycogen metabolism in isolated hepatocyte suspensions favoured glycogenolysis and under no conditions was net glycogen synthesis observed. Gluconeogenesis from added precursors was difficult to discern with fed chicken hepatocytes due to the high basal glucose production but was readily demonstrated at a constant rate over a two hour incubation with starved chicken hepatocytes.

The gluconeogenic effectiveness of precursors was generally similar in isolated hepatocytes and in chickens in vivo. The greater effectiveness of lactate compared with pyruvate, observed with both systems (unlike the rat), is probably a consequence of impaired hydrogen ion transfer during pyruvate gluconeogenesis due to the mitochondrial location of phosphoenolpyruvate carbcxykinase in the chicken. Synergistic interactions between substrates were shown to occur and be important for interpretation of results from isolated hepatocytes for extrapolation to the situation in vivo. Glycerol was

Physiological concentrations of glucagon stimulated glycogenolysis and gluconeogenesis from precursors entering the glycolytic pathway above and below the triose phosphate dehydrogenase step. Although it was possible to assign a glucagon control point between triose phosphate and glucose in chicken liver, that between pyruvate and phosphoenol pyruvate (postulated for the rat) was not observed.