The Effects of the Natriuretic Factor from Uremic Urine

a significant and substantial fall in short-circuit current and potential difference was observed. The changes began after a lag period of at least 10 min and continued over a period of 60 min. The decrease in short-circuit current at the end of 1 h averaged 44%. The same fraction from the urine of normal subjects produced no significant change in either short-circuit current or potential difference. When the isolated epithelial cells from the toad bladder were incubated in the presence of the inhibitor, intracellular sodium content increased significantly. There was no change in intracellular water content; hence the intracellular concentration of sodium increased by a mean of 7 meq/liter. The changes in intracellular potassium content and concentration were not statistically significant. When the isolated epithelia were incubated with the uremic factor, there was also a significant decrease in pyruvate utilization in relation to cells from paired hemibladders incubated in the absence of the fraction. The fraction from normal subjects produced no change in either intracellular sodium content or pyruvate oxidation. The results suggest that the inhibitor acts from the serosal surface, inhibits sodium transport across the This work has been published in abstract form in the Abstracts of the 6th Annual Meeting of the American Society of Nephrology, 1973. Dr. Bourgoignie is the recipient of U. S. Public Health Service Research Career Development Award 7 KO 4HL40977 and Dr. Kaplan is supported by U. S. Public Health Service Fellowship Award 5 F02-AM,53772. Received for publication 2 October 1973 and in revised form 21 January 1974. serosal barrier, and produces a decrease in substrate utilization in association with the change in transepithelial sodium transport.