Angiotensin-converting enzyme inhibitors and angiotensin-II-receptor antagonists modulate sodium handling based on endogenous lithium clearance.

Background: Numerous studies based on assessment of lithium clearance demonstrated higher sodium reabsorption in renal proximal tubules in individuals with hypertension, overweight, obesity, metabolic syndrome, or diabetes.
Aims: We aimed to assess the influence of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin-II-receptor antagonists (ARB) treatment on sodium handling.
Methods: In a sample of 351Caucasian subjects without diuretic treatment with prevailing sodium consumption, we studied associations between renal sodium reabsorption in proximal (FPRNa) and distal (FDRNa) tubules assessed by endogenous lithium clearance and daily sodium intake measured by 24-hour excretion of sodium (UNaV), in the context of obesity and long-term treatment with ACE-I or ARB.
Results: In the entire study population, we found a strong negative association between FPRNa and ACE-I/ARB treatment (b = -19.5; SE = 4.9; P <0.001). Subjects with FPRNa above the median value showed a significant adverse association between FPRNa and age (b = -0.06; SE = 0.02; P = 0.003), with no association with ACE-I/ARB treatment (P = 0.68). In contrast, in subjects with FPRNa below the median value, we found a strongly significant adverse relationship between FPRNa and ACE-I/ARB treatment (b = -30.4; SE = 8.60; P <0.001), with no association with age (P = 0.32).
Conclusions: ACE-I/ARB long-term treatment modulates FPRNa in the group with lower reabsorption, but not in that with higher than median value for the entire study population.