The Role of Circulating Natriuretic and Diuretic Factors, including Urea

or returned to the circulation (as in UO-reinf rats), exert a diuretic effect. In additional experiments, UO rats infused with urea exhibited post-obstructive diuresis, if extracellular volume contraction was prevented. This result suggests that urea may be an important diuretic factor in post-obstructive diuresis, but does not exclude possible roles for other humoral factors. The intact kidney of UO-reinf rats displayed a massive unilateral diuresis and natriuresis, further suggesting the presence of potent diuretic factors in the urine. A marked increase in the fractional excretion of glomerular filtrate (V/GFR) by the intact kidney This work was presented in part at the 6th Annual Meeting of the American Society of Nephrology, Washington, D. C., November, 1973. Dr. Harris is a Veterans Administration Research and Education Associate. Received for publication 21 March 1975 and in revised form 27 May 1975. suggests that this diuresis may be attributable, in part, to impaired proximal reabsorption.