INTRAUTERINE GROWTH-RETARDATION DUE TO GROWTH-HORMONE DEFICIENCY IN RATS

The effect of growth hormone (GH) on fetal growth was examined in the spontaneous dwarf rat (SDR) with the isolated GH deficiency. A 328-bp GH gene fragment containing the site of SDR mutation was amplified fro m fetal liver genomic DNA using PCR and digested with restriction enzy me SauI to distinguish the fetal genotype. When heterozygote (dr/+) ma les and females were crossed, a significant reduction in body weight o f dr/dr fetuses was observed on days 20 and 21 (92 and 89% that of +/ fetuses, respectively). Body weight reduction was also noticed on day 21 in dr/dr fetuses (80%) in comparison with that of dr/+ fetuses cro ssed from dr/dr females and dr/+ males. Unexpectedly, the body weight of dr/+ fetuses was found to be significantly less than that of +/+ fe tuses on days 19 (94%) and 20 (97%), which reached the level of +/+ fe tuses by day 21 of gestation. The fetal tail length was not affected b y the GH status. These results provide direct evidence for the involve ment of pituitary GH in the regulation of fetal body weight during lat e gestation, but not in fetal skeletal growth.