Differential responses to prenatal malnutrition among neonatal rats

Female rats were fed (A) protein-restricted diet 1 month prior to mating and throughout pregnancy, or (B) protein-free diet during 10-20 days of pregnancy. At birth, four parameters of the offspring, body weight, cerebral weight, cerebral DNA, and cerebral protein were well correlated with each other, and were significantly lower than in the controls fed stock diet. The malnourished population had on the average 30-70% "outstanding low" individuals (parameter values more than 2 SD below the mean of the control); this is 13-20 times more than in the control. Even in malnourished populations a certain number of individuals escaped malnutrition (parameter values not lower than the mean of the control): they appear to be those which in normal populations would be well above the average. These individuals escaped malnutrition not by taking advantage of their littermates: the latter, though malnourished, were still better than the average in the malnourished group. The mechanisms by which some of the malnourished females differentially provide enough nutrients for one of their fetuses, and more than the average for its littermates, may involve differential mobilization of maternal nutrient among individual mothers, as well as differential blood supply to individual placentas or placental transfer to individual fetuses.