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 ϩ transporters, viz., the NaϪ cotransporter in the thick ascending limb and the Na ϩ -Cl Ϫ 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 ϩ 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 ϩ -K ϩ -2Cl Ϫ cotransporter and all three subunits of the epithelial Na ϩ channel (ENaC) were increased by furosemide infusion. HCTZ infusion increased the abundances of thiazide-sensitive Na ϩ -Cl

Antidiuretic Effect of Hydrochlorothiazide in Lithium-Induced Nephrogenic Diabetes Insipidus Is Associated with Upregulation of Aquaporin-2, Na-Cl Co-transporter, and Epithelial Sodium Channel

“…In this study, the abundance of NCC in distal convoluted tubule was not altered by Li administration but increased by HCTZ treatment in Li-induced NDI rats. This result can be interpreted in light of the notion from our previous studies: (1) aldosterone upregulates the expression of NCC (20), and (2) chronic HCTZ treatment induces a compensatory increase in the abundance of NCC (13).…”

“…For chronic HCTZ treatment for 7 d, osmotic minipumps (model 2ML1; Alzet, Palo Alto, CA) were implanted subcutaneously to deliver 3.75 mg/d HCTZ (YuHan Corp., Seoul, Korea) as described previously (13). HCTZ was dissolved in a 1.7% ethanolamine solution, and the minipumps that contained vehicle (ethanolamine) alone were implanted in vehicle-treated rats.…”

Role of the alternative splice variant of NCC in blood pressure control

“…Hence, the NCC abundance in uEV was analyzed in these patients following treatment with thiazide diuretics, the main anti-hypertensive drug. In line with several studies in animal models [72,73], NCC abundance was increased after thiazide treatment [70]. Furthermore, pre-treatment abundance of NCC in uEVs correlated with blood pressure response to thiazide diuretics, which implies that this method could be used to predict patients’ thiazide sensitivity.…”

Everything we always wanted to know about furosemide but were afraid to ask

“…Indeed, long-term use of furosemide can increase the abundance of NKCC2 in the thick ascending limb and OAT1 in the proximal tubule (84). Furthermore, furosemide infusion increases the abundance of all three subunits of the epithelial Na ϩ channel in connecting tubules, cortical collecting ducts, outer medullary collecting ducts, and inner medullary collecting ducts (108). Chronic furosemide administration has also been associated with an increased Na ϩ -K ϩ -ATPase expression in the distal convoluted tubule and in cortical collecting duct (135), suggesting the possibility of enhanced capacity in sodium reabsorption in these segments.…”