The contribution of glucose to neonatal glucose homeostasis in the lamb

• Published in: Metabolism, clinical and experimental clinical and experimental, 1998-10, Vol.47 (10), p.1239-1244
• Main Authors: Cowett, Richard M., Rapoza, Robert E., Gelardi, Nancy L.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn - metabolism; Biological and medical sciences; Carbohydrates; Fundamental and applied biological sciences. Psychology; Glucagon - blood; Glucose - metabolism; Homeostasis; Hydrocortisone - blood; Insulin - blood; Metabolisms and neurohumoral controls; Sheep; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0026-0495; 1532-8600
• DOI: 10.1016/S0026-0495(98)90330-4

A multiplicity of substrates and hormones interact to influence neonatal glucose homeostasis. Based on prior studies in our laboratory, we hypothesized that glucose alone does not tightly control neonatal glucose homeostasis. Fifteen spontaneously delivered, mixed-breed term lambs, weighing 4.7 ± 0.9 kg (mean ± SD) were studied at 4.7 ± 0.6 days after birth following administration of 100 μCi d[6,6- 3H 2] glucose in 0.9% NaCl by the prime plus constant fusion technique to measure glucose production. After a baseline period, five lambs received 8.5 mg · kg −1 · min −1 glucose in combination with the following to isolate the contribution of glucose: somatostatin to block insulin, glucagon, and growth hormone release; metyrapone to block cortisol release; phentolamine to block α-adrenergic release; and propranolol to block β-adrenergic release (glucose + blockade). Five lambs received the above without the glucose infusion (blockade). Five lams continued to receive 0.9% NaCl alone as the diluent for the isotopic tracer throughout the study (control). The glucose + blockade group had a significant increase in plasma glucose ( P < .0001) and a significant increase in total glucose appearance ( P < .0001) compared with both the blockade and control groups. Under conditions of glucose infusion at a rate 49% greater than the basal rate, the endogenous glucose production rate persisted such that there was only an evanescent decrease compared with that of the control group, which was not statistically different over time. As a substrate, glucose does not tightly control neonatal glucose homeostasis.