INFLUENCE OF AN ENRICHED DIETARY-SODIUM CHLORIDE REGIME DURING GESTATION AND SUCKLING AND POST-NATALLY ON THE ONTOGENY OF HYPERTENSION IN THE RAT

Brattleboro rats with diabetes insipidus were subjected to sodium chloride enrichment (20-fold increase in dietary salt) at various stages of their development. Salt supplementation in the adult rat produced higher systolic blood pressure (SBP), particularly in males (142 .+-. 3 versus 110 .+-. 3 mmHg in control. The blood pressures of females on salt-supplemented diets during pregnancy decreased from 136 .+-. 1 to 121 .+-. 2 mmHg, although throughout this period the blood pressures for these rats were greater than for the control pregnant rats. Pregnant females on salt-supplemented diets also showed higher sodium concentrations in the amniotic fluid compared with controls (155 .+-. 3.4 versus 134.1 .+-. 6.0 mmol/l). Salt supplemented lactating mothers produced milk with similar sodium concentrations to those of the controls, but the urinary sodium concentrations of pups sucking on the former were greater than in the controls. It is concluded that the suckling pups were also salt-enriched. Rats were submitted to salt-enriched regimes in utero, during suckling, post-weaning and post-pubertally, or permutations thereof. Salt supplementation post-weaning led to consistent elevation in arterial blood pressure with males being more susceptible than females. The degree of elevation was increased if the salt-supplement was present during suckling (132 .+-. 1 versus 112 .+-. 1 mmHg) and was greatest when the salt-supplemented regime were administered both in utero and during the post-weaning period (154 .+-. 2 versus 112 .+-. 1 mmHg). Rats exposed to salt enrichment in utero, or in utero and during suckling, but fed a control diet post-weaning and into adulthood did not develop hypertension as adults. Indeed, in some these rats showed a lower blood pressure than control animals which had the regular diet throughout their life from conception to adulthood. Of the hormones which were measured, the most relevant was perhaps 18-OH-DOC which showed a specific sex difference in animals on the control diets (males: 17.9 .+-. 3.6 ng/ml; females: 86.4 .+-. 14.0 mg/ml). Furthermore, 18-OH-DOC concentrations were increased in females on salt-enriched diets but not in males on the same diet (females: 156.4 .+-. 16.5 ng/ml; males: 18.6 .+-. 2.1 ng/ml).