Effects of somatostatin and glucose infusion on glucose kinetics in fetal sheep.

We examined the contribution of glucose, independently of insulin, on fetal glucose kinetics in the sheep by infusing somatostatin (SRIF), followed by SRIF plus glucose (protocol A) or reversing the initial infusion sequence (protocol B). In protocol A (n = 8), infusion of SRIF at 200 micrograms/h decreased plasma insulin (IRI) and blood glucose (G) by 2.8 +/- 1.0 microU/ml and 1.34 +/- 0.2 mg/dl from their respective basal concentrations of 6.8 +/- 1.4 microU/ml and 16.47 +/- 0.91 mg/dl (P less than 0.05; P less than 0.005). There were no significant changes in plasma glucagon (IRG) or the rates of umbilical G uptake or of G utilization, but G turnover decreased by 1.77 +/- 0.34 mg.kg-1.min-1 (P less than 0.005). Addition of G at a rate of 5.6 +/- 0.8 mg.kg-1.min-1 had no effect on IRI and IRG. Total G uptake (G infusion rate plus umbilical G uptake) increased from 6.37 +/- 0.77 to 10.25 +/- 1.0 mg.kg-1.min-1 (P less than 0.01), despite suppression of umbilical G uptake by 33%. Fetal G reached a new steady state of 23.08 +/- 1.37 mg/dl, and G turnover increased by 4.81 +/- 0.96 mg.kg-1.min-1 from its SRIF-induced nadir (P less than 0.005). Since G concentration was maintained at steady state, the rate of G utilization was equivalent to the rate of total G uptake, an increase of 60% from basal despite suppressed IRI.(ABSTRACT TRUNCATED AT 250 WORDS)