Blocking T-Type Ca2+ Channels with Efonidipine Decreased Plasma Aldosterone Concentration in Healthy Volunteers

Efonidipine can block both L- and T- type Ca 2+ channels. In a previous in vitro study, we clarified that efonidipine dramatically suppresses aldosterone secretion from human adrenocortical tumor cells during angiotensin II (Ang II)− and K + -stimulation, whereas nifedipine, a dominant L-type Ca 2+ channel antagonist, does not. This study was conducted to assess the in vivo effects of efonidipine and nilvadipine on the plasma aldosterone concentration. Placebo, 40 mg of efonidipine, or 2 mg of nilvadipine was administered to five healthy male volunteers. Hemodynamic parameters (pulse rate [PR] and blood pressure [BP]), plasma concentrations of neurohormonal factors (plasma renin activity, Ang II, aldosterone, and adrenocorticotropic hormone [ACTH]), and serum concentrations of Na + and K + were measured before and 6 h after administration of the agents. All three agents had little effect on PR and BP. Efonidipine and nilvadipine significantly increased plasma renin activity and Ang II. Both had little effect on ACTH, Na + , and K + . The plasma aldosterone concentration was significantly decreased after efonidipine treatment (88.3±21.3 to 81.6±24.9 pg/ml, p =0.0407), whereas it was significantly increased after nilvadipine treatment (66.5±12.2 to 82.17±16.6 pg/ml, p =0.0049). Placebo had little effect on neurohormonal factors. Efonidipine decreased plasma aldosterone concentration despite the increase in plasma renin activity and Ang II, suggesting that T-type Ca 2+ channels may also play an essential role in the secretion of aldosterone in healthy human volunteers.