Effects of calcium antagonism on the resting and exercise-stimulated renin-aldosterone axis

The effect of short-term calcium antagonism with felodipine on blood pressure and on some biochemical plasma variables such as catecholamines, renin and aldosterone was studied in 10 normal volunteers at rest and during incremental bicycle exercise. At rest, diastolic blood pressure was slightly decreased during felodipine, whereas systolic pressure and heart rate were not significantly changed. The plasma noradrenaline concentration and plasma renin activity were increased during felodipine treatment; the plasma adrenaline and aldosterone concentrations on the contrary, were not significantly changed. The rises in plasma renin activity, plasma aldosterone and plasma adrenaline and noradrenaline concentrations produced by exercise were not significantly affected by felodipine. The plasma calcium concentration was significantly higher during felodipine treatment than during placebo and this was accompanied by an increased urinary calcium excretion. It is concluded that the rise in plasma renin activity during calcium antagonism with felodipine is not accompanied by a significant increase in plasma aldosterone. Furthermore, the present data suggest that, at least during exercise, calcium antagonism does not interfere with the mechanisms underlying the exercise-induced activation of renin and aldosterone release.