Effects of varying severity of growth retardation on organ weight and cell population in foetal rats.

Abstract

Recent experiemental studies have shown that a growth-retarding stress applied early in life results in diminished cell populations of all organs whereas a similar stress applied later on causes reduction predominately in cell size. The object of the present study was to determine the effects on cell size and population of organs of varying the severity of stress at a single time interval in pregnancy. Unilateral uterine ischemia was induced surgically in rats on the 17th day of pregnancy to produce a range of fetuses with birth weight reduced by up to 45% of the values for fetuses from the control uterine horns. Cell size and populatins at term were estimated from the figures for organ weight and total DNA. A close correlation was shown between the severity of growth retardation and the degree of reduction in organ weight and cell population although the size of the effect varied for different organs. Reduction in fetal weight by 45% reduced liver weight by 60% and liver cell population by 50%, whereas brain weight was reduced by only 20% reduction in cell population. No consistent change was seen in weight or cell population of the placenta. It is concluded that for a growth-retarding stress acting at a sing;e time interval in pregnancy the reduction in cell size and populations of different interval organs is directly related to the reduction in birth weight.