Increased renal Na-K-ATPase, NCC, and beta-ENaC abundance in obese Zucker rats

Renal sodium retention, as a result of increased abundance of sodium transp orters, may play a role in the development and/or maintenance of the increa sed blood pressure in obesity. To address this hypothesis, we evaluated the relative abundances of renal sodium transporters in lean an obese Zucker r ats at 2 and 4 mo of age by semiquantitative immunoblotting. Mean systolic blood pressure was higher in obese rats relative to lean at 3 mo, P < 0.02. Furthermore, circulating insulin levels were 6- or 13-fold higher in obese rats compared with lean at 2 or 4 mo of age, respectively. The abundances of the <alpha>(1)-subunit of Na-K-ATPase, the thiazide-sensitive Na-CI cotr ansporter NCC or TSC), and the beta -subunit of the epithelial sodium chann el (ENaC) were all significantly increased in the obese rats' kidneys. Ther e were no differences for the sodium hydrogen exchanger (NHE3), the bumetan ide-sensitive Na-K-2Cl cotransporter (NKCC2 or BSC1), the type II sodium-ph osphate cotransporter (NaPi-2), or the a-subunit of ENaC. These selective i ncreases could possibly increase sodium retention by the kidney and therefo re could play a role in obesity-related hypertension. sodium-phosphate cotr ansporter type II; sodium-hydrogen exchanger type III; bumetanide-sensitive sodium-potassium-2 chloride cotransporter; insulin resistance; hypertensio n; sodium-chloride cotransporter; epithelial sodium channel; adenosine 5'-t riphosphatase.