PERINATAL ENERGY STORES AND EXCESSIVE FAT DEPOSITION IN GENETICALLY-OBESE (FA FA) RATS/

To find out whether perinatal differences in energy stores are essenti al for the phenotypic manifestation of the fa/fa genotype in 16-day-ol d rats, we investigated Zucker rats (13M) x Brown Norway (BN) hybrids. +/fa and fa/fa hybrids were identified by molecular polymorphisms sim ilar to 1 cM from the fa locus. The fat content of all pups increased rapidly after birth, and differences between +/fa and fa/fa hybrid pup s were significant in 7- and 16-day-old rats but not at 0, 1, and 4 da ys of age. For 16-day-old 13MBN hybrids as well as 13M Zucker rats, pl ots of carcass fat vs. body mass were closely fitted by parallel regre ssion lines, with carcass fat similarily higher in fa/fa than +/fa pup s of both strains. Fetal and neonatal plasma insulin concentration and hepatic glycogen in the 13MBN hybrid pups did not differ between +/fa and fa/fa littermates, nor did the hepatic and adipose tissue triglyc erides in 24-h-old 13MBN hybrid pups. The manifest differences between fatty and lean 16-day-old pups thus do not depend on differences in p erinatal energy stores.