WEANLING RATS EXPOSED TO MATERNAL LOW-PROTEIN DIETS DURING DISCRETE PERIODS OF GESTATION EXHIBIT DIFFERING SEVERITY OF HYPERTENSION

1. In the rat, hypertension is induced by fetal exposure to maternal l ow-protein diets, The effect on blood pressure of undernutrition befor e conception and during discrete periods in early, mid or late pregnan cy was assessed using an 18% casein (control) diet and a 9% casein die t to apply mild protein restriction. 2. The offspring of rats fed 9% c asein developed raised blood pressure by weaning age, Feeding a low-pr otein diet before conception was not prerequisite for programming of h ypertension. 3. Hypertension was observed in rats exposed to low prote in during the following gestational periods: days 0-7, days 8-14 and d ays 15-22. Blood pressure increases elicited by these discrete periods of undernutrition were Lower than those induced by feeding a low-prot ein diet throughout pregnancy, The effect in early gestation;was signi ficant only in male animals, Post-natal growth of male rats exposed to low-protein diets was accelerated, but kidneys were small in relation to body weight. 4. Biochemical indices of glucocorticoid action in li ver, hippocampus, hypothalamus and lung were elevated in rats exposed to low-protein diets in utero, The apparent hypersensitivity to glucoc orticoids was primarily associated with undernutrition in mid to late gestation. 5. Plasma renin activity was elevated in rats exposed to 9% casein over days 15-22 of gestation, Animals undernourished over days 0-7 and 8-14 produced pups with lower plasma angiotensin II concentra tions at weaning. 6. Fetal exposure to maternal low-protein diets for any period in gestation may programme hypertension in the rat, Alterat ions to renal structure, renal hormone action or the hypothalamic-pitu itary-adrenal axis may all play a role in the programming phenomenon, either independently or in concert.