Dietary salt affects fluid intake and output patterns of pregnant rats

This study was done to determine how differences in dietary NaCl influence water and electrolyte balance during gestation. Eighteen adult female rats were fed diets containing either 0.12 (low), 1.0 (mid, control), or 3.0% (high) NaCl throughout gestation. On gestation days 1-19, body weight, water and food intakes, urine volume and electrolyte levels were measured. On gestation day 20, amniotic fluid electrolyte levels were determined; litter sizes were assessed 24-hr after birth. Because food intakes were similar throughout gestation, the dams of the three groups ingested different amounts of NaCl. Differences in dietary NaCl were accompanied by large differences in the daily patterns of urine sodium, urine sodium/potassium ratios, water intake, and urine volume. Despite these differences in intake and output, water and electrolyte balance (intake minus output) was the same for the three groups. There were no differences in the dams' body weights, amniotic fluid electrolyte levels, or litter sizes. The long-term consequences of perinatal dietary NaCl for the developing pups are discussed.