Abstract
Summary
In anesthetized dogs the fractional excretion of urea was measured during antrdiuresis and mannitol diuresis when the glomerular nitration rate was either normal or reduced by inflation of a balloon in the aorta above the renal arteries. Reductions in glomerular filtration rate to 70% or less of normal values resulted in a significant reduction in the fractional urea excretion to 50% of normal values during antidiuresis but caused no significant changes during diuresis. Increased passive reabsorption of urea occurring as a result of increased transit time of tubular fluid is the proposed explanation for the changes in fractional urea excretion.
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