Thiazide diuretic receptors: Autoradiographic localization in rat kidney with (/sup 3/H)metolazone

Journal Article · Sat Jul 01 04:00:00 EDT 1989 · J. Pharmacol. Exp. Ther.; (United States)

OSTI ID:5603985

Beaumont, K; Vaughn, D A; Healy, D P

The localization of binding sites for (/sup 3/H)metolazone, a quinazolinesulfonamide diuretic with thiazide-like actions, was determined by in vitro autoradiography. (/sup 3/H)Metolazone bound saturably to rat kidney sections incubated in vitro with a dissociation constant (Kd) = 3.4 nM and binding site density = 0.14 pmol/mg of protein. Incubation conditions were used that excluded binding to low affinity sites and carbonic anhydrase. Pharmacological specificity of binding was consistent with labeling of physiologically relevant thiazide diuretic receptors, as identified in previous studies of (/sup 3/H)metolazone binding to renal membranes. Autoradiographs obtained with tritium-sensitive film demonstrated that binding sites were limited to the renal cortex and were relatively sparsely distributed. Higher resolution autoradiography indicated that (/sup 3/H) metolazone binding sites were localized in a highly specific manner over short lengths of tubular segments, which by their morphology and distribution most likely represented distal convoluted tubules. In the short sections of tubule that contained receptors, labeling was very dense and appeared to be more prevalent over luminal than peritubular surfaces. The intrarenal distribution of (/sup 3/H)metolazone binding sites provides further evidence for their identity as thiazide diuretic receptors. These results are consistent with physiological studies demonstrating that the early distal tubule is the location of thiazide-sensitive sodium chloride cotransport.

• Research Organization: Univ. of California, San Diego (USA)
• OSTI ID: 5603985
• Journal Information: J. Pharmacol. Exp. Ther.; (United States), Journal Name: J. Pharmacol. Exp. Ther.; (United States) Vol. 250:1; ISSN JPETA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AUTORADIOGRAPHY
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL LOCALIZATION
BODY
CELL CONSTITUENTS
CELL MEMBRANES
DIURETICS
DRUGS
KIDNEYS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
TRITIUM COMPOUNDS
VERTEBRATES