Enzymatic adaptations in newborn pig liver

Abstract Numerous studies during the neonatal period in the rat have demonstrated that many changes occur in the activities of liver enzymes of carbohydrate metabolism especially those of glycolysis, gluconeogenesis, and glycogen synthesis and degradation. Such information, however, has not been available in the newborn pig. The present study of several regulatory enzymes was undertaken to determine if an enzymatic defect could explain fasting hypoglycemia in the newborn pig. The hepatic liver enzymes, non-specific hexokinase, glucokinase, glucose-6-phosphatase, UDPG: α-glucan glucosyltransferase, phosphorylase, phosphofructokinase, aldolase, fructose diphosphatase, and phosphopyruvate carboxylase have been measured in developing pig liver. The activity of all hepatic enzymes except hexokinase were low in fetal tissue and increased after birth in livers from both fed and fasted pigs. Hexokinase activity was present prior to birth and remained essentially unchanged after birth and was not affected by prolonged starvation. Liver glycogen was rapidly mobilized at birth in both fed and fasted newborn animals. It is concluded that a defect in enzymes measured under the stated assay conditions does not exist and can not be offered as an explanation for the observed fasting hypoglycemia in newborn pigs.