In the present study the hypotensive mechanism of AdM (13-52) was investigated in rats, both in vitro and in vivo. It was found that the hypotensive effect of AdM (13-52) could be partially inhibited by L-NG-nitro-arginine (LNNA), an inhibitor of nitric oxide synthase. The vasodilator effect of AdM (13-52) was dependent on vascular endothelium and inhibited by LNNA in a dose-dependent manner. This LNNA induced inhibitory effect could be reversed with L-Asginine. In addition, the vasodilator effect of AdM (1...