Mild exercise activates renal dopamine system in mild hypertensives

Abstract

Objective: The role of renal dopamine in the early depressor effect of exercise was evaluated in hypertensives. Methods: After a general clinical observation period of 4 weeks, 29 essential hypertensives were divided into two groups. The exercise group (n = 16) underwent blood lactate threshold exercise using a cycle ergometer for 60 min three times a week for 4 weeks. Results: In the non-exercise group (n = 13), blood pressure (BP) and humoral variables did not change significantly (from 150 ± 3/93 ± 2 to 145 ± 2/94 ± 1 mm Hg). In the exercise group (n = 16), resting BP was significantly reduced from 158 ± 2/92 ± 2 at week 0 to 145 ± 3/85 ± 3 mm Hg at week 4. The increase in urinary free dopamine excretion (from 248 ± 14 to 276 ± 24 ng/mg Cr) at week 4 was significantly higher than that in the non-exercise group (from 220 ± 31 to 196 ± 27 ng/mg Cr). In the exercise group, urinary kallikrein activity also increased significantly from 173.0 ± 35.4 at week 0 to 320.3 ± 63.3 ng bradykinin/min/mg Cr at week 4. These changes in urinary free dopamine excretion and urinary kallikrein activity were negatively correlated with the change in BP. The change in urinary sodium excretion was also negatively correlated with the change in plasma volume index. Moreover, the change in urinary free dopamine excretion was positively correlated with the changes in urinary kallikrein activity and urinary sodium excretion. The change in renal decarboxylation rate of DOPA (3,4-dihydroxyphenylalanine) positively correlated with the changes in urinary free dopamine excretion and urinary sodium excretion, and was negatively correlated with the change in systolic BP. Conclusion: These results suggest that exercise triggered renal dopamine generation and activation of renal kallikrein-kinin system, resulting in natriuresis and BP reduction in the early phase (4 weeks) of mild exercise.