title: Upregulation of Na+ transporter abundances in response to chronic thiazide or loop diuretic treatment in rats.
abstract: Furosemide and hydrochlorothiazide (HCTZ) exert their diuretic actions by binding to apical Na(+) transporters, viz., the Na(+)-K(+)-2Cl(-) cotransporter in the thick ascending limb and the Na(+)-Cl(-) cotransporter in the distal convoluted tubule, respectively. We carried out semiquantitative immunoblotting and immunohistochemistry of rat kidneys to investigate whether chronic administration of furosemide or HCTZ is associated with compensatory changes in the abundance of Na(+) transporters downstream from the primary site of action. Osmotic minipumps were implanted into Sprague-Dawley rats to deliver furosemide (12 mg/day) or HCTZ (3.75 mg/day) for 7 days. To prevent volume depletion, all animals were offered tap water and a solution containing 0.8% NaCl and 0.1% KCl as drinking fluid. The diuretic/natriuretic response was quantified in response to both agents by using quantitative urine collections. Semiquantitative immunoblotting revealed that the abundances of thick ascending limb Na(+)-K(+)-2Cl(-) cotransporter and all three subunits of the epithelial Na(+) channel (ENaC) were increased by furosemide infusion. HCTZ infusion increased the abundances of thiazide-sensitive Na(+)-Cl(-) cotransporter and beta-ENaC in the cortex and beta- and gamma-ENaC in the outer medulla. Consistent with these results, beta-ENaC immunohistochemistry showed a remarkable increase in immunoreactivity in the principal cells of collecting ducts with either diuretic treatment. These increases in the abundance of Na(+) transporters in response to chronic diuretic treatment may account for the generation of diuretic tolerance associated with long-term diuretic use.
authors.affiliation: Department of Internal Medicine, Seoul National University, Clinical Research Institute of Seoul National University Hospital, South Korea.
authors.forename: Ki Young
authors.initials: KY
authors.lastname: Na
authors.forename: Yoon Kyu
authors.initials: YK
authors.lastname: Oh
authors.forename: Jin Suk
authors.initials: JS
authors.lastname: Han
authors.forename: Kwon Wook
authors.initials: KW
authors.lastname: Joo
authors.forename: Jung Sang
authors.initials: JS
authors.lastname: Lee
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Earm
authors.forename: Mark A
authors.initials: MA
authors.lastname: Knepper
authors.forename: Gheun-Ho
authors.initials: GH
authors.lastname: Kim
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004232:Diuretics / Q000494:pharmacology; D053503:Epithelial Sodium Channels; D005665:Furosemide / Q000494:pharmacology; D006852:Hydrochlorothiazide / Q000494:pharmacology*; D007150:Immunohistochemistry; D007685:Kidney Tubules, Collecting / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008138:Loop of Henle / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000032:analysis / Q000378:metabolism*; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology*; D028021:Sodium-Potassium-Chloride Symporters / Q000032:analysis / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D004232:Diuretics; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D049993:Sodium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D006852:Hydrochlorothiazide; D005665:Furosemide