Ontogeny of the insulin response to glucose in fetal and adult sheep.
The purpose of the present experiments was to examine in sheep whether the fetal insulin response to glucose was present by day 110 (d110) of pregnancy and whether the magnitude of the fetal insulin response changed between d110 and d145 (term). We also compared the responses observed in fetuses to those of adult nonpregnant sheep. Basal concentrations of glucose measured in plasma collected from the fetal femoral artery rose progressively between d110 and d145 of gestation, but did not attain the plasma glucose concentrations measured in adult sheep. Peak glucose concentrations in fetuses were achieved 10 min following the bolus injection of glucose (0.8 g/kg estimated fetal body weight) into the fetal femoral vein, and peak values increased with gestational age. Significantly higher peak glucose concentrations were achieved in adult sheep. The concentration of insulin rose rapidly in fetuses at d110, and a similar time course of insulin release in plasma was seen at all gestational ages. The peak plasma insulin concentrations were achieved at 20 min and were significantly greater in older (d140-145) than younger (d125-130) fetuses (p less than 0.05). Peak insulin values in fetuses were much less than in adult sheep. In adult sheep glucose and insulin concentrations remained elevated at 120 min following the injection of glucose, whereas in the fetus the concentration of insulin had returned to preinjection values by 60 min. The insulin/glucose ratio did not change in fetal lambs over the last one third of gestation and was not different from the adult sheep.(ABSTRACT TRUNCATED AT 250 WORDS)
Houghton
P E
PE
Medical Research Council Group in Reproductive Biology, Lawson Research Institute, St. Joseph's Health Center, London, Ont., Canada.
McDonald
T J
TJ
Challis
J R
JR
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004285:Dogs; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000097:blood*; D011247:Pregnancy; D012756:Sheep / Q000254:growth & development* / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin; D005947:Glucose