Renal sympathetic nerve activity (RSNA) and adrenergic stimulation increase Na‐Cl cotransporter (NCC) phosphorylation and trafficking to the apical plasma membrane (APM)

Abstract

RSNA plays a primary role in hypertension (HTN) pathogenesis: RSNA is increased in models of HTN, renal denervation alleviates HTN, and RSNA promotes Na reabsorption. Distal convoluted tubule (DCT) NCC reabsorbs only 5–10% of filtered NaCl yet NCC is a key blood pressure (BP), fluid and electrolyte control point: genetic or chemical inhibition of NCC provokes salt wasting and lowers BP while NCC activation can cause HTN. This study tested the hypothesis that acute RSNA and/or adrenergic stimulation increase the number of active NCC in the DCT APM. One of two stimulation protocols (and shams) was applied in Sprague Dawley rats: 1) RSNA was acutely increased by injecting 50 μl phenol into the cortex, 2) α1 agonist phenylephrine (PE, 10 mg/kg, 10–20 min) was infused into one renal artery. After the protocols, kidneys were removed and subjected to density gradient fractionation to resolve low density APM from high density intracellular membranes (ICM). 12 fractions were collected and assayed by immunoblot with anti-NCC and anti-NCCp antibodies. Both stimuli provoked redistribution of 20% of the total NCC from higher into lower density fractions enriched in APM. PE doubled the NCCp/total ratio in the APM fractions. These results demonstrate that activation of DCT NCC, mediated by trafficking and phosphorylation, may contribute to the anti-natriuretic, BP raising effects of RSNA. Supported by DK083785, ASN Scherbenske award