A B S T R A C T The urine of patients with chronic uremia contains a gel filtration fraction that is natriuretic in the rat. The effects of this fraction on the isolated urinary bladder of the toad were examined in the present studies. When added to the serosal surface of the bladder, 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 pro- INTRODUCTIONThe effector element of the biologic control system which regulates the renal excretion of sodium is believed to be multifaceted and to have several component parts (1-3). Among these is a postulated natriuretic hormone which theoretically could play a central role in modulating the rate of sodium excretion.In previous studies, we have described an inhibitor of sodium transport in the serum of patients with advanced chronic renal disease (4,5). This serum factor was found to inhibit sodium transport by the isolated frog skin and toad bladder (4) and to produce natriuresis in rats with a reduced nephron population (5). More recently, the same gel filtration fraction obtained from urine of patients with chronic uremia has been found to possess natriuretic activity in the rat (6).In the present studies, attempts have been made to derive information about the site and mechanism of action of the urinary inhibitor using the isolated bladder of the toad. The toad bladder lends itself well to this type of study for several reasons. First, the serum factor inhibits transepithelial sodium transport by the anuran bladder, and the urine factor, if it is the same substance, should have similar inhibitory capabilities. Second, isolated epithelial cells removed from the intact toad bladder have been used recently to investigate the site of action of inhibitors of sodium transport (7). Inhibitors that act at the serosal surface of the epithelia (e.g. ouabain) increase intracellular sodium content, while those acting at the mucosal surface (e.g., amiloride) have the opposite effect (7). Third, the isolated The Journal of Clinical Investigation Volume 53 June 1974-1568-1577 1568 epithelial cell prepa...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.