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

C. A. Bloch, R. K. Menon, M. A. Sperling

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Abstract

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 μg/h decreased plasma insulin (IRI) and blood glucose (G) by 2.8 ± 1.0 μU/ml and 1.34 ± 0.2 mg/dl from their respective basal concentrations of 6.8 ± 1.4 μU/ml and 16.47 ± 0.91 mg/dl (P < 0.05; P < 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 < 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 < 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 < 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. In protocol B (n = 7), during combined G and SRIF infusion, the changes in hormone and G concentrations, as well as G fluxes and kinetics were quantitatively similar to those in protocol A. We conclude that in fetal sheep a large fraction of glucose can be utilized in the absence of insulin stimulation.

Original languageEnglish
Pages (from-to)18/1
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume255
Issue number1
StatePublished - 1988
Externally publishedYes

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