Afferent Renal Nerve Activity Drives Chlorthalidone-Induced Salt Intake

Background: High salt intake is a global public health concern and is linked to the development of hypertension, kidney disease, and millions of preventable deaths annually. Despite recommendations to reduce salt intake, the average daily intake remains more than double the American Heart Association’s recommended limit. We have shown that afferent renal denervation (ARDN) significantly reduces salt intake in DOCA-salt rats. Here, we tested the hypothesis that Epithelial Sodium Channel (ENaC) mediated sodium reabsorption in the collecting duct increases afferent renal nerve activity (ARNA) and drives increased salt intake. Methods: We assessed salt intake using two bottle preference tests, in which rats had access to dH2O and 1.8% NaCl for 14 days. Chlorthalidone (CTD) was used to inhibit NCC and increase both sodium delivery to the collecting duct and ENaC activity. 5 groups of male (M) and female (F) Sprague Dawley rats (10–14 weeks old) were studied: Vehicle (peanut butter, p.o; n=9M, 6F), CTD (5 mg/kg, p.o; n=9M, 6F), CTD-ARDN (n=6M, 7F), CTD-Amiloride (CTD + 10 mg/kg AMI, p.o; n=8M, 6F), and CTD-ARDN-AMI (n=6M, 6F). ARDN was performed bilaterally (33 mM periaxonal capsaicin). Results: Relative to vehicle, CTD significantly increased saline intake in both male and female rats (M: P<0.001, F: P=0.002) without affecting water intake (M: P=0.992, F P=0.984). ARDN reduced CTD-induced saline intake (M: P=0.006, F: P<0.001) with no effect on water intake. Amiloride similarly reduced CTD-induced saline intake (M: P<0.001, F: P<0.001). ARDN and amiloride in combination did not have an additive effect compared to either treatment alone, suggestive of a common mechanism of action. (CTD-ARDN vs. CTD-ARDN-AMI: M: P=0.272, F: P=1.000; CTD-AMI vs. CTD-ARDN-AMI: M: P=0.555, F: P=0.712). In additional anesthetized male rats (n=3 per group), resting ARNA was recorded after 14 days of two bottle preference tests. CTD markedly increased baseline ARNA in male rats. Baseline ARNA was 62.2% maximum in CTD rats, compared to 9.8% in vehicle-treated rats. CTD induced increases in ARNA were reduced by co-treatment with amiloride to 27.8%. Conclusion: These studies support the hypothesis that ARDN decreases salt intake through an ENaC dependent mechanism, potentially leading to a novel treatment for high salt intake. Funding: Other NIH Support - National Heart, Lung, and Blood Institute (NHLBI)