Impaired growth and increased glucocorticoid-sensitive enzyme activities in tissues of rat fetuses exposed to maternal low protein diets.

Epidemiological evidence that hypertension and coronary heart disease are programmed by exposure to poor diet during intrauterine life, is supported by animal experiments. In the rat, fetal exposure to a maternal low protein diet is associated with abnormal fetal growth and later elevation of blood pressure. Fetal exposure to glucocorticoids of maternal origin are proposed to underlie this association. Pregnant female rats were fed control (18% casein) or moderately low protein diets (9% casein). Feeding of low protein was either throughout gestation (d0-22), or for specific periods (d0-7, d8-14, d15-22). Fetal and placental weight were determined at d14, 20 and 22. Low protein feeding in the periods d0-7, d8-14, d0-14 stimulated fetal growth to d14. At d20 gestation low protein exposed fetuses tended to be smaller than control fetuses, although low protein d8-14 fetuses were significantly larger than controls. Animals exposed to low protein diets were of lower weight at birth and had higher blood pressure at 4 weeks postnatal age. The activities of glucocorticoid-inducible enzymes in brain (fetal and neonatal) and liver (neonatal) were specifically elevated relative to control animals, by low protein exposure. The data suggest that low protein exposure, particularly in late gestation is associated with increased fetal glucocorticoid-exposure. This may both retard fetal growth and programme later increases in systolic blood pressure.