Early Administration of Angiotensin-Converting Enzyme Inhibitor Captopril, Prevents the Development of Hypertension Programmed by Intrauterine Exposure to a Maternal Low-Protein Diet in the Rat

Abstract

1. Associations of intrauterine exposure to maternal undernutrition with later hypertension and coronary heart disease in the human population have been duplicated in the rat. Fetal exposure to low protein diets produces offspring that develop raised systolic blood pressure by the age of weaning. This animal model of ‘programmed’ hypertension was used to investigate the role of the renin—angiotensin system in the initiation and maintenance of high blood pressure. 2. Pregnant rats were fed diets containing 18 or 9% casein from conception until littering. The offspring from these pregnancies were administered captopril either between 2 and 4 weeks of age, or from 10 to 12 weeks of age. 3. The feeding of low protein diets in pregnancy had no effect upon the reproductive ability of female rats and the offspring generated were of normal birthweight. By 4 weeks of age the male and female offspring of low-protein-fed dams had systolic blood pressures that were 24–25 mmHg higher than those of rats exposed to a control diet in utero. 4. Treatment of 10-week-old female offspring with captopril for 2 weeks indicated that angiotensin II formation may play a role in the maintenance of high blood pressure in low-protein-exposed rats. While captopril had no significant effect upon systolic pressures of rats exposed to the control diet in intrauterine life, the systolic blood pressures of low-protein animals rapidly declined by 31 mmHg. 5. Administration of captopril to male and female offspring between 2 and 4 weeks of age exerted long-term effects upon systolic blood pressure. Eight weeks after cessation of treatment, at an age where maximal blood pressures are achieved, captopriltreated, low-protein-exposed rats had similar blood pressures to normotensive rats exposed to the protein-replete diet in utero. 6. In conclusion, we have demonstrated that the elevation of adult blood pressure associated with fetal exposure to a maternal low-protein diet, is prevented by early administration of an angiotensin-converting enzyme inhibitor. The actions of angiotensin II in the late suckling period may be a critical determinant of long-term cardiovascular functions in these animals.