DEVELOPMENTAL SENSITIVITY TO HIGH DIETARY-SODIUM CHLORIDE IN BORDERLINE HYPERTENSIVE RATS

The present study compared the postweaning blood pressures and body we ights of borderline hypertensive rats exposed to a high (8%) sodium ch loride maternal diet either from conception to weaning or only during the weaning period with borderline hypertensive rats consistently expo sed to a normal (1%) sodium chloride maternal diet. Because the effect s of early sodium chloride exposure may be most evident during a subse quent challenge, rats from each group were assigned to receive either an 8% sodium chloride or a 1% sodium chloride diet from 8 to 17 weeks of age. Exposure to an 8% sodium chloride diet from conception through weaning increased the adult blood pressure of borderline hypertensive rats compared with that of controls exposed to a 1% sodium chloride d iet; exposure to an 8% sodium chloride diet only during weaning did no t increase blood pressure. An 8% sodium chloride diet beginning at 8 w eeks of age increased systolic blood pressure. The effects of perinata l and adult exposure to high dietary sodium chloride were additive. Be havioral observations and urinary electrolyte measures confirmed that pups exposed to an 8% sodium chloride diet during weaning ingested the high-sodium chloride diet. The blood pressure and heart rate response s to autonomic nervous system ganglionic blockade were assessed at 17 weeks of age. Borderline hypertensive rats exposed to an 8% sodium chl oride diet from conception through weaning showed an increased bradyca rdic response, but no difference in depressor response, to ganglionic blockade. These data suggest that the window of developmental sensitiv ity for modulation of blood pressure regulation by high dietary sodium chloride occurs during prenatal and early postnatal development.