Effect of fructose-induced hypoglycemia on cessation of macromolecular transport in the neonatal calf.

Fructose was used as a hypoglycemic agent to determine whether availability of glucose during early life mediates the cessation of intestinal transport of Ig (closure). Either glucose or fructose (100 g in 2 L of electrolyte solution) was fed to calves deprived of colostrum at 3, 6, 9, 12, 15, 18, and 21 h postpartum. Colostrum (1 kg) was fed to all calves at 24, 36, and 48 h postpartum. Venous blood was sampled, and plasma was harvested, for the measurement of glucose, fructose, insulin, and IgG. During the first 24 h, means for plasma glucose from calves treated with glucose and fructose, respectively, were 282 and 24 mg/dl. The latter value reflects the degree of hypoglycemia induced by feeding fructose. During the same period, corresponding concentrations of plasma fructose were 4 and 230 mg/dl. Plasma insulin concentrations for precolostral calves were 101 and 11 microU/ml for calves treated with glucose and fructose, respectively. Peak IgG concentrations were extremely low for both groups of calves, indicating that intestinal transport of Ig had virtually ceased by the end of the 24-h treatment period. Thus, fructose-induced hypoglycemia had no effect on the time of intestinal closure in the newborn calf.