THE TUBULAR REABSORPTION OF UREA, THIOUREA AND DERIVATIVES OF THIOUREA IN THE DOG KIDNEY

Abstract

The renal plasma clearance of each of the following compounds, thiourea, methylthiourea, phenylthiourea or s-diethylthiourea, was detd. with the simultaneous area and creatinine clearance. The % of water which was reabsorbed in the tubules had a pronounced effect upon the % of urea, thiourea and the derivatives of thiourea which were reabsorbed. From low to high % of water reabsorbed, 61-99% of the s-diethylthiourea, 28-93% of the phenylthiourea, 29-87% of the methylthiourea, 20-59 % of the thiourea, and 18-60% of the urea filtered at the glomeruli were reabsorbed. The striking exaltation of the clearance, evoked by an acceleration of the rate of urine flow, occurred later with thiourea than with urea, but was not observed at all with the derivatives of thiourea. The % of thiourea and urea reabsorbed were approx. the same during decreasing or slowly increasing rate of urine flow. The % of each derivative of thiourea reabsorbed was always less than the % of urea reabsorbed during the same interval of time, and at normal, low rates of urine flow the methylthiourea clearance was about 50%, the phenylthiourea clearance was about 20%, and the s-diethylthiourea clearance was about 3% of the simultaneous urea clearance. The reabsorption of thiourea and of each of its derivatives was independent of the plasma conc. obtained of each substance respectively. The relative magnitudes of the % of thiourea and the derivatives of thiourea reabsorbed directly corresponded to the chemical structures of the molecules, with reference to the substituted and un-substituted amino groups, and was related to the ratios of water-solubility to ether-solubility of the compounds.