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Testosterone metabolism in rabbits actively immunized with testosterone
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.
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.