Maternal nutrient storage and efficiency in production of fetal brain tissue in rats.

Maternal 'efficiencies' in production of fetal tissue, especially brain tissue, were studied in controls and in chronically (9 generations) undernourished rats. These 'efficiencies' were formulated as the ratio of a neonatal parameter (body) weight, brain weight, DNA, or protein) to the food consumed during pregnancy. Mean or total values (for the entire litter) of the above parameters were used in computation of the above ratios. It was found that all these ratios were highly significantly lower for control animals than for undernourished. The gain in maternal body weight (postpartum versus day 0 of pregnancy), i.e., nutrient storage, was found to be significantly lower or even negative in the undernourished group, but increased through generations. We interpret these results as follows. Undernourished animals mobile their nutrient reserves, avoid deamination of essential amino acids, and improve their intestinal absorption of nutrients; thus, they are more efficient than normal animals, even though the latter may produce more fetal tissue. These improvements suggest inducible enzymes. Individual mothers in each group vary considerably in their efficiency; the most efficient undernourished mothers may produce offspring that escape undernutrition, or, in the control group, offspring with outstanding values of brain and body parameters.