Growth and cellular composition in rats with intrauterine growth retardation: effects of postnatal nutrition.

We evaluated the catch-up growth of rats with intrauterine growth retardation (IUGR) raised in normal litters (8-10 pups) or in large litters (14-16 pups) during the first 2 wk of life. We also studied the influence of nutrition on cellular composition at birth and at 2 wk. Fifty-four pups (27 IUGR and 27 controls) were enrolled into normal or undernutrition groups. Postnatal undernutrition resulted in significantly lower growth in both control and IUGR rat pups than in normally fed pups. In the control group, postnatal undernutrition resulted in a lower liver weight but not a lower brain weight. Underfeeding of the IUGR group produced a greater number of cells of the brain and liver, but with smaller cell size than in normally fed IUGR rats. We conclude that compensatory catch-up growth in the mild-IUGR rat occurs if the postnatal nutrition is adequate. When postnatal nutrition is restricted, the non-IUGR rats became malnourished at 2 wk of age and the mild-IUGR rats did not demonstrate the catch-up growth phenomenon as was seen in those with adequate nutrition. In the severe-IUGR rat, undernutrition further compromised growth rate, so that at 2 wk of age their weights were the lowest of all the groups studied.