THE EFFECTS OF PANCREATECTOMY ON THE RATES OF GLUCOSE UTILIZATION, OXIDATION AND PRODUCTION IN THE SHEEP FETUS

Abstract

The effects of fetal pancreatectomy on the uptake and metabolism of glucose were investigated in chronically catheterized sheep fetuses during late gestation by using tracer methodology. Rates of glucose uptake and metabolism were also measured in pancreatectomized fetuses during the infusion of insulin. Pancreatectomy produced hypoinsulinaemia and significantly reduced the rates of fetal glucose utilization and umbilical glucose uptake in comparison to intact fetuses of a similar gestational age. There was no significant alteration in the glucose oxidation fraction after pancreatectomy but because glucose utilization was low in the pancreatectomized fetuses, the rate of fetal glucose oxidation was significantly less after pancreatectomy than in intact animals. No apparent endogenous production of glucose was observed in the pancreatectomized fetuses. Insulin infusin into the pancreatectomized fetuses raised the rates of umbilical glucose uptake and of fetal glucose utilization and oxidation by 40-50% to values similar to those observed in intact animals. The endogenous production of glucose remained negligible during the infusion of insulin into the pancreatectomized fetuses. There was a net flux of radioactive glucose from the pancreatectomized fetus to the uteroplacental tissues and from the uteroplacental tissues into the uterine circulation. These net fluxes and the rate of placental metabolism of tracer glucose decreased significantly during the infusion of insulin into the pancreatectomized fetus. When all the data were combined, partial correlation analysis of the net uteroplacental uptake of tracer glucose and the fetal concentrations of plasma insulin and blood glucose showed that the fetal arterial glucose concentration was the major influence on the net flux of tracer from the fetus to the uteroplacental tissues. These observations demonstate that the endogenous concentration of insulin has an important role in regulating glucose metabolism in sheep fetus during late gestation.