Differences in perinatal NaCl exposure alters blood pressure levels of adult rats.

To determine the effect of differences in NaCl intake early in development on adult blood pressure levels, adult Sprague-Dawley female rats were maintained on diets containing either 0.12, 1.0, or 3.0% dietary NaCl throughout pregnancy and lactation. The offspring were continued on these same diets to 30 days postpartum. Thereafter, all offspring were maintained on the same stock diet containing 1% NaCl. Beginning at 60 days, systolic blood pressure and heart rate were measured weekly for the next 6 wk by tail-cuff plethysmography in lightly etherized rats. Mean arterial pressure (MAP) and heart responses to the subcutaneous sequential administration of 100 micrograms/kg angiotensin II and 15 micrograms/kg isoproterenol were then obtained from the catheterized femoral or carotid artery in awake unrestrained rats. Rats raised on 3% NaCl diet had significantly higher base-line MAPS (127.1 mmHg) than rats raised on the 1% (117.4 mmHg) or 0.12% (115.8 mmHg) salt diets. The highest salt group was also significantly more responsive to the pressor effects of angiotensin II (+46.4 mmHg) and the depressor effects of isoproterenol (-41.4 mmHg) than the mid- (+35.6 and -32.2 mmHg) and low- (+26.9 and -32.5 mmHg) salt groups. Thus there is a sensitive period early in ontogenesis of the normotensive Sprague-Dawley rat during which blood pressure and blood pressure responsiveness to angiotensin II and isoproterenol may be influenced permanently by dietary NaCl.