title: Testosterone metabolism in rabbits actively immunized with testosterone.
abstract: Active immunization of male rabbits results in a marked increase in plasma testosterone (T) and in the fraction of T bound to circulating proteins. In order to identify the cause of the increased T levels, the half-life of T after castration, and the metabolic clearance rate (MCR) and production rate (PR) after a single injection of tritiated T were determined in normal and immunized rabbits. In the immunized animals the half-life of T was significantly longer, the MCR showed a 10-fold decrease (10.2 +/- 3.2 1/day compared to 108 +/- 43 1/day) and the PR was increased from 0.44 +/- 0.34 mg/day to 1.20 +/- 0.36 mg/day compared with the control group. The binding of T to circulating antibodies is considered to be the direct cause of the decreased MCR and, via the diminished negative feedback at the hypothalamic-pituitary levels, the indirect cause of the increased PR in the immunized animals.
mesh_terms: D000818:Animals; D001666:Binding Sites, Antibody; D002369:Castration; D007110:Immunity, Active; D008297:Male; D008657:Metabolic Clearance Rate; D013739:Testosterone / Q000097:blood / Q000276:immunology / Q000378:metabolism*
chemical_list: D013739:Testosterone