BMR, DNA AND CELL SIZE IN PRE- AND POSTNATALLY DEPRIVED RATS

Abstract

In Infants BMRs are lower In prenatal than in postnatal onset growth failure. The significance of this was Investigated In rats with similar types of growth failure by relating their BMR to body velght (BWt), combined organ (O: liver, kidney, heart, and brain) weight (OWt), DNA (ODNA), and protein (OPr). Mature rats were fed a 6% protein diet 1 month prior to and during mating, gestation, and lactation. Offsprings were fed 27% protein at weaning (A). Offsprings of normal rats were fed low protein from weaning to 10 weeks and high protein up to weight recovery (6). The Insult caused permanent stunting In group A rats; ¾ of group B rats had normal weights by 24 weeks. Sleeping BMRs were measured In 4 rats of each group before sacrificing, at weaning, 10, 16, and >16 weeks, and in litter-mates weekly up to maturity. The relation of the BMR with BWt, OWt, and OPr was curvl-linear; that with ODNA was linear. These relations were similar for normal controls. The BMR per BWt, OWt, and OPr decreased with age as cell size Increased. The insults affected ODNA and OPr of liver, kidney, and heart in both groups but not of brain. Recovery paralleled weight recovery. Recovery of cell size occurred first. The data show that the BMR reflects cell number rather than cell mass. Comparison of the BMRs suggests that the Insult of group A rats was not comparable to that which caused dwarfing In Infants with growth failure of prenatal onset.