THE CONTRIBUTION OF GLUCOSE TO NEONATAL GLUCOSE-HOMEOSTASIS IN THE LAMB

A multiplicity of substrates and hormones interact to influence neonat al glucose homeostasis. Based on prior studies in our laboratory, we h ypothesized that glucose alone does not tightly control neonatal gluco se homeostasis. Fifteen spontaneously delivered, mixed-breed term lamb s, weighing 4.7 +/- 0.9 kg (mean +/- SD) were studied at 4.7 +/- 0.6 d ays after birth following administration of 100 mu Ci D[6,6-H-3(2)] gl ucose in 0.9% NaCl by the prime plus constant infusion technique to me asure glucose production. After a baseline period, five lambs received 8.5 mg.kg(-1).min(-1) glucose in combination with the following to is olate the contribution of glucose: somatostatin to block insulin, gluc agon, and growth hormone release; metyrapone to block cortisol release ; phentolamine to block alpha-adrenergic release; and propranolol to b lock beta-adrenergic release (glucose + blockade). Five lambs received the above without the glucose infusion (blockade). Five lambs continu ed to receive 0.9% NaCl alone as the diluent for the isotopic tracer t hroughout the study (control). The glucose + blockade group had a sign ificant increase in plasma glucose (P < .0001) and a significant incre ase in total glucose appearance (P < .0001) compared with both the blo ckade and control groups. Under conditions of glucose infusion at a ra te 49% greater than the basal rate, the endogenous glucose production rate persisted such that there was only an evanescent decrease compare d with that of the control group, which was not statistically differen t over time. As a substrate, glucose does not tightly control neonatal glucose homeostasis.