Prematurity in the rat. III. Effect of oxygen supply

Changes in liver glycogen, plasma glucose, lactate, alanine and glycerol concentrations in term and preterm newborn rats breathing pure oxygen have been studied. The time courses of lactate and pyruvate concentrations in the livers of term and preterm rats breathing air or pure oxygen have also been investigated. The increased oxygen supply enhanced plasma glucose, lactate and alanine utilization while the rate of glycogenolysis was not effected. In these conditions, the resistance to lactate utilization observed in preterm newborns breathing air was overcome. The liver lactate/pyruvate ratio sharply decreased immediately after delivery in term and preterm rats breathing pure oxygen and in term rats breathing air. However, this decrease was delayed for 30 min in preterm newborns breathing air. These results suggest that the preterm rat suffers a defective oxygen supply to the tissues which results in a transient resistance to lactate utilization.