AJP - Endocrinology and Metabolism, Vol 272, Issue 1 E68-E73, Copyright © 1997 by American Physiological Society
Separate and joint effects of arginine and glucose on ovine fetal insulin secretion
A. Gresores, S. Anderson, D. Hood, G. O. Zerbe and W. W. Hay Jr
Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA.
To determine separate and joint effects of increases (delta) in fetal
plasma concentrations of arginine (Af) and glucose (Gf) on fetal insulin
(If) secretion (delta If), 15 late-gestation fetal sheep were given 5-min
arginine bolus infusions (40, 86, 144, 201, and 402 mumol/kg estimated
fetal wt) at 90 min of 120 min steady-state glucose clamps (basal Gf, basal
+ 0.6 mM Gf, and basal + 1.1 mM Gr), producing absolute and percent
increases above basal Af of 25.8 +/- 1.3 microM (+33%), 50.9 +/- 6.3 microM
(+66%), 83.8 +/- 7.1 microM (+108%), 122.1 +/- 9.4 microM (+156%), and
302.2 +/- 28.2 microM (+386%), respectively. Acute hyperglycemia alone
produced an increase above basal If of 9 +/- I microU/ml (+80%) and 19 +/-
2 microU/ml (+170%) after basal + 0.6 mM Gf and basal + 1.1 mM Gf,
respectively. Increasing values of delta Af showed separate but lesser
effects on delta If, which were significant only at very high values of Af
(> 100% above mean normal Af) unless marked hyperglycemia (1.5- to
2-fold normal) was also present, demonstrating joint effects of delta Af
and delta Gf on delta If according to a best-fit inverse polynomial
response surface. We conclude that physiological increases in Af at normal
glucose concentrations are not a potent-stimulus to insulin secretion in
fetal sheep.
