AJP - Renal Physiology, Vol 258, Issue 4 908-F915, Copyright © 1990 by American Physiological Society

ARTICLES

Effect of ions on binding of the thiazide-type diuretic metolazone to kidney membrane

J. M. Tran, M. A. Farrell and D. D. Fanestil
Department of Medicine, University of California, San Diego, La Jolla 92093.

The effect of a number of ions on the binding of the thiazide-type diuretic metolazone (MTZ) to rat renal cortical membranes was studied to elucidate the mechanism of NaCl transport in the kidney distal tubule. Among the cations tested, Na+ significantly stimulated the binding up to 2.4-fold over control. The effective concentration of Na+ that produced half-maximal stimulation was 2-17 mM. Li+, K+, NH4+, Rb+, and Cs+ produced little stimulation of binding of MTZ. Several anions including Cl- inhibited binding. The inhibition of binding of MTZ by Cl- was enhanced by Na+ and Li+. Scatchard analyses revealed that 50 mM Na+ increased the affinity for binding of MTZ from a Kd = 3.56 +/- 0.15 nM to Kd = 1.32 +/- 0.11 nM. Chloride, in the presence of 50 mM Na+, competitively inhibited binding of MTZ by suppressing the affinity to Kd = 9.27 +/- 1.11 nM without changing the maximal number of binding sites (0.733 +/- 0.049 pmol/mg). A mechanism for the MTZ-sensitive NaCl transport is proposed, in which the transporter protein possesses a binding site for Na+ and a binding site for Cl-, which is also the binding site for MTZ. Na+ binds to its site and increases the affinity for Cl-/MTZ. The binding of Cl- to the transporter enables the import of Na+ and Cl- across the tubule membrane. MTZ, however, when present competes with Cl- for the binding site on the transporter and prevents the transport of Na+ and Cl-.

This article has been cited by other articles:

				E. Moreno, P. S. Cristobal, M. Rivera, N. Vazquez, N. A. Bobadilla, and G. Gamba Affinity-defining Domains in the Na-Cl Cotransporter: A DIFFERENT LOCATION FOR Cl- AND THIAZIDE BINDING J. Biol. Chem., June 23, 2006; 281(25): 17266 - 17275. [Abstract] [Full Text] [PDF]

				A. Paredes, C. Plata, M. Rivera, E. Moreno, N. Vazquez, R. Munoz-Clares, S. C. Hebert, and G. Gamba Activity of the renal Na+-K+-2Cl- cotransporter is reduced by mutagenesis of N-glycosylation sites: role for protein surface charge in Cl- transport Am J Physiol Renal Physiol, May 1, 2006; 290(5): F1094 - F1102. [Abstract] [Full Text] [PDF]

				A. M. Weinstein A mathematical model of rat distal convoluted tubule. I. Cotransporter function in early DCT Am J Physiol Renal Physiol, October 1, 2005; 289(4): F699 - F720. [Abstract] [Full Text] [PDF]

				G. Gamba Molecular Physiology and Pathophysiology of Electroneutral Cation-Chloride Cotransporters Physiol Rev, April 1, 2005; 85(2): 423 - 493. [Abstract] [Full Text] [PDF]

				E. Sabath, P. Meade, J. Berkman, P. d. l. Heros, E. Moreno, N. A. Bobadilla, N. Vazquez, D. H. Ellison, and G. Gamba Pathophysiology of functional mutations of the thiazide-sensitive Na-Cl cotransporter in Gitelman disease Am J Physiol Renal Physiol, August 1, 2004; 287(2): F195 - F203. [Abstract] [Full Text] [PDF]

				A. J. Magaldi New insights into the paradoxical effect of thiazides in diabetes insipidus therapy Nephrol. Dial. Transplant., December 1, 2000; 15(12): 1903 - 1905. [Full Text] [PDF]

				A. Monroy, C. Plata, S. C. Hebert, and G. Gamba Characterization of the thiazide-sensitive Na+-Cl- cotransporter: a new model for ions and diuretics interaction Am J Physiol Renal Physiol, July 1, 2000; 279(1): F161 - F169. [Abstract] [Full Text] [PDF]

				K. R. Cesar and A. J. Magaldi Thiazide induces water absorption in the inner medullary collecting duct of normal and Brattleboro rats Am J Physiol Renal Physiol, November 1, 1999; 277(5): F756 - F760. [Abstract] [Full Text] [PDF]

				H. Chang and T. Fujita A kinetic model of the thiazide-sensitive Na-Cl cotransporter Am J Physiol Renal Physiol, June 1, 1999; 276(6): F952 - F959. [Abstract] [Full Text] [PDF]

				D. D. Fanestil, D. A. Vaughn, and P. Blakely Dietary NaCl and KCl do not regulate renal density of the thiazide diuretic receptor Am J Physiol Regulatory Integrative Comp Physiol, October 1, 1997; 273(4): R1241 - R1245. [Abstract] [Full Text] [PDF]

				N. Vazquez, A. Monroy, E. Dorantes, R. A. Munoz-Clares, and G. Gamba Functional differences between flounder and rat thiazide-sensitive Na-Cl cotransporter Am J Physiol Renal Physiol, April 1, 2002; 282(4): F599 - F607. [Abstract] [Full Text] [PDF]