Effect of castration and testosterone treatment on catecholamine metabolism in ventral prostates of normal and chemically sympathectomized rats

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Abstract
In addition to marked atrophy, castration significantly lowered the endogenous contents of norepinephrine, dopamine, and the synthesizing enzyme tyrosine hydroxylase (EC 1.14.16.2) in the rat ventral prostate. Orchidectomy also markedly reduced the total amount of essential amino acid, tyrosine, the precursor of catecholamine. The changes in these constituents seemed to be androgen-dependent since testosterone (50 mg/kg) replacement for 3 days, beginning from the 4th day of castration, restored various parameters related to monoamine metabolism to values seen in normal rats. Intravenous injections of 6-hydroxydopamine resulted in significant decreases in norepinephrine content and tyrosine hydroxylase activity of the ventral prostate of rats killed on the 11th day after the beginning of treatment. In contrast, the endogenous levels of dopamine and tyrosine per prostate were markedly increased after the administration of 6-hydroxydopamine.A group of rats intended to undergo gonadectomy was injected with two doses of 6-hydroxydopamine (50 mg/kg; 12 h apart) 4 days before castration. These animals were subsequently injected with two doses of 6-hydroxydopamine (100 mg/kg; 12 h apart) 1 day after castration (i.e., the 5th day after the first 6-hydroxydopamine treatment) and killed 6 days after gonadectomy (i.e., the 11th day after the first injection of 6-hydroxydopamine). Administration of 6-hydroxydopamine to castrated rats produced changes similar to those seen in animals with intact testicles, except that the magnitude of changes in norepinephrine, tyrosine hydroxylase, and dopamine content was more pronounced. Even though testosterone treatment in orchidectomized rats previously treated with 6-hydroxydopamine significantly increased tyrosine hydroxylase and norepinephrine levels per prostate, it never restored these adrenergic nerve constituents to normal values. However, both dopamine and tyrosine contents were enhanced well above the values seen in normal rats. Our data suggest that intact nerve supply to the prostate may be important in mediation of the effects of testosterone on the metabolism of its various adrenergic nerve constituents.