Mechanism of renal excretion of methylurea and acetamide in the dog

¹ Department of Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina

The renal excretion of methylurea, acetamide, and urea was studied in anesthetized dogs during a graded osmotic diuresis produced by infusion of mannitol, urea, methylurea, or acetamide. Within the urine-to-plasma inulin range of 3–300, the clearances of these compounds relative to the inulin clearance were less than 1.0 while their urine-to-plasma ratios were greater than 1.0. For all compounds the urine-to-plasma ratios and the amount reabsorbed were directly related to water reabsorption. No dependence of reabsorption on filtered load and no transport maxima at high filtered loads were observed. These results suggest reabsorption of all three compounds by passive transport and indicate the absence of a quantitatively appreciable active secretion or reabsorption.

Key Words: urea • passive transport • organic nonelectrolytes

Submitted on November 16, 1964