Some Effects of High and Low Sodium Intake During Pregnancy in the Rat

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Abstract
Histological examinations of the kidney and adrenal were made to determine whether sodium conservation during pregnancy in the rat is related to the degree of granulation of the juxtaglomerular cells of the kidney, considered indicative of renin secretion, and whether this, in turn, influences the width of the zona glomerulosa, considered indicative of aldosterone secretion. Pregnant animals receiving low, moderate and high levels of dietary sodium were studied along with nonpregnant controls. Determination of sodium and potassium retention and the concentration of sodium and potassium in plasma and muscle provided essential supporting data for interpretation of the histological findings. Both pregnancy and decreasing levels of sodium intake led to an increase in juxtaglomerular granulation and in zona glomerulosa width. In all but the low sodium pregnant group, in which there was evidence of sodium deficiency, an increase in juxtaglomerular granulation was accompanied by an increase in zona glomerulosa width and in the percentage of dietary sodium conserved by the kidney. The low sodium pregnant group had less juxtaglomerular granulation than the corresponding nonpregnant group or the other pregnant groups. Despite this degranulation, the low sodium pregnant animals had the widest zona glomerulosa and conserved the greatest percentage of dietary sodium. It is suggested that in this group juxtaglomerular degranulation was due to a rate of renin secretion exceeding the rate of production, thereby reducing the number of secretory granules present in the cells.