Involvement of increased arginase activity in the impaired cavernosal relaxation with aging in the rabbit

Tokyo Med. Dent. Univ. , 3)Inst. Biomater. Bioengin. , Tokyo Med. Dent. Univ. We examined whether arginase is involved in the impaired cavemosal relaxation with aging. Cavemosal tissues obtained from young and aged rabbits were used for isometric tension experiments, measurements of cGMP production, NOS and arginase activities, endogenous methylarginines and L-arginine. CCh produced endothelial NO-dependent relaxation, which was significantly impaired in the aged group without change in SNP-induced relaxation. Stimulated cGMP production was significantly decreased in the aged group. NOS activity per se remained unchanged in two groups. Tissue contents of methylarginines and L-arginine were decreased in the aged group. Arginase activity was significantly higher in the aged group. The impaired CCh-induced relaxation in the aged group was normalized by NOHA as an arginase inhibitor or by the excess L-arginine. These results suggest that the impaired endothelial NO-dependent cavemosal relaxation with aging is due to the decreased NO production, which would result from the increased arginase activity and probably from the decreased L-arginine content.