1. Because studies of the metabolic problems of the human intra-uterine growth-retarded neonate are limited by ethical considerations we have used the intra-uterine growth-retarded piglet as an animal model. Total body-glucose kinetics were measured in 16 intra-uterine growth-retarded and 11 normal piglets from the same litters with [3H]glucose as a tracer.
2. The intra-uterine growth-retarded animals had marginally smaller brains than their normal littermates, but substantially smaller livers. Liver weight was reduced in proportion to body weight.
3. Total body-glucose turnover rate was significantly lower (P < 0.001) in the intra-uterine growth-retarded animals in comparison with their normal littermates, but was appropriate for their smaller body and liver weights. Brain weight was only slightly reduced in the intra-uterine growth-retarded group so that glucose turnover adjusted to a common brain weight was significantly lower (P < 0.001) in these animals.
4. Total body-glucose pool size was lower in the intra-uterine growth-retarded animals (P < 0.01), but was appropriate for their body and liver weights. It was significantly reduced in relation to brain weight (P < 0.001).
5. Resting plasma glucose concentration was lower in the intra-uterine growth-retarded animals (P < 0.001). There was no relationship between concentration and turnover in either group.
6. It is suggested that the observed differences in total body-glucose turnover may be associated with profound differences in cerebral metabolism in the intra-uterine growth-retarded animals.