Biphasic effects of orchidectomy on calcitonin gene-related peptide synthesis and release.

We hypothesize that the decline of male gonadal hormones may play a role in age-related decrease of calcitonin gene-related peptide (CGRP) synthesis and release. Orchidectomized rats were raised with or without testosterone replacement and CGRP levels in serum and some tissues as well as the perfusate from the isolated mesenteric arterial bed (MAB) were measured at 1, 2 and 4 months after orchidectomy. CGRP levels of serum and tissues, and CGRP release from MAB were significantly elevated after 1 month and decreased after 4 months in orchidectomized rats. The changes were restored by testosterone replacement. Our results indicate that the age-related decline of testosterone might contribute to the age-related decrease of CGRP synthesis and release.