Some Effects of High and Low Sodium Intakes during Pregnancy in the Rat

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Abstract
Pregnant animals fed the low sodium diet showed general langour and debility, ate less food and gained less weight than those receiving control or high sodium intakes. Sodium and potassium retentions were greater in pregnant groups than nonpregnant, but significantly smaller retentions were observed for animals receiving the low sodium intake as compared with those receiving higher intakes. A smaller percentage of ingested sodium and potassium was excreted by pregnant groups than nonpregnant. A marked conservation of urinary sodium was observed for all animals fed the low sodium diet. When the level of dietary sodium was increased, sodium excreted by the kidney was increased indicating that animals could regulate renal excretion of dietary sodium 10 times greater than the control level. Significant decreases in hematocrit levels and concentrations of hemoglobin and plasma total protein in pregnant groups appeared to be associated with hemodilution which normally accompanies pregnancy. The significantly smaller over-all decreases in hematocrit and in concentrations of hemoglobin and total protein in the low sodium group were probably reflections of decreased blood volume associated with sodium depletion. Significant decreases in the concentrations of all protein fractions, excepting gamma globulin, were observed in pregnant groups and were related to the increased blood volume of normal pregnancy. The smaller over-all decreases in these fractions in pregnant animals fed the low sodium diet wee associated with less expansion of blood volume. The significant increase in the percentage of alpha1 globulin and the decrease in gamma globulin in pregnant groups suggested that these changes were true effects of pregnancy and independent of blood volume fluctuations. The level of dietary sodium did not have a significant effect on reproductive performance as evaluated by the number of live young, number of resorptions, fetal weight and placental/fetal ratios. These data indicate that the adverse effects observed in the maternal organism occurred in an effort to maintain normalcy of the fetus. These effects were pronounced in animals maintained with low sodium but no adverse effects were observable when the maternal animal received a high sodium intake during the gestation period.