Urinary dopamine, sodium handling, and blood pressure in a bi-ethnic South African population: the SABPA study.

Abstract

Introduction: Urinary dopamine is associated with increased sodium excretion in experimental studies, and possibly contributes to blood pressure (BP) regulation and salts-ensitivity. Studies in humans are limited, and the potential association with potassium is unclear. We aimed to compare urinary dopamine/creatinine ratio and investigate the associations of urinary dopamine/creatinine ratio with BP, sodium, potassium, and sodium/potassium ratio (Na/K) in Black and White adults.

Methods: We included Black (n = 160) and White (n = 197) men and women aged 20-65 years. We recorded 24-hour BP, measured urinary dopamine and creatinine, and calculated their ratio. Urinary sodium and potassium were measured, and Na/K ratio calculated.

Results: Urinary dopamine/creatinine ratio was lower in the Black group (p = 0.030) as compared to the White group, while urinary dopamine metabolites were higher in the Black group (p ≤ 0.001) compared to the White group. In multiple regression analyses, the following significant associations were confirmed: urinary dopamine/creatinine ratio associated positively with sodium and potassium in both the Black and White groups (all ß ≥ 0.296; p < 0.001) and negatively with Na/K ratio (ß = -0.285; p < 0.001) only in the Black group. No associations were observed between urinary dopamine/creatinine ratio and BP.

Conclusion: The lower levels of urinary dopamine in the Black group as compared to their White counterparts could be explained by the higher urinary dopamine metabolite levels in the Black group, due to a possible higher rate in the metabolism of urinary dopamine and low potassium levels observed in this group. The unique negative association between urinary dopamine and Na/K_{-_}ratio only in the Black participants suggest that potassium may contribute significantly to the renal sodium-handling properties of renal dopamine in Black populations.