Effect of hypotonic expansion on sodium, water, and urea excretion in late pregnancy: the influence of posture on these results

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Abstract

Mineralocorticoid-treated, normotensive third trimester subjects positioned in lateral recumbency were studied before and during the infusion of 300 mEq of hypotonic saline. Urinary sodium excretion increased in all subjects from a mean value of 199 to 416 μEq/min. In 12 maximally hydrated subjects free water clearance (CH2O) and urine flow (V) increased from means of 7.54 and 9.50 to 11.6 and 14.5 ml/100 ml of glomerular filtrate (GFR) Also the ratio of urea to inulin clearance (Curea/Cinulin) increased from 0.59 to 0.64. The changes in the renal handling of water and urea suggest that fractional sodium reabsorption decreased at proximal nephron sites.

Authors

Marshall D. Lindheimer, Peter V. Weston