Uptake, binding and metabolism of testosterone in rat brain tissues

Abstract

Slices of cerebral cortex, pituitary and hypothalamus of one-day castrated adult male rats were incubated with tritiated testosterone (T), and the ventral prostate was used as a control target organ. Uptake seemed to be a non-specific process of exchange diffusion. Tissue specificity appeared in macromolecular binding and intracellular metabolism of the hormone. Pituitary tissue bound testosterone less and much more slowly than did prostatic tissue, but the binding was greater than that observed in hypothalamus and cerebral cortex. Moreover, the percentage of bound hormone in nuclear extracts of hypothalamus, and especially pituitary, appeared to be dependent on its concentration in the medium. The main metabolite found in the prostate was dihydrotesterone (DHT). In the pituitary less DHT was found, but the rate of conversion of T to DHT remained far higher than in hypothalamus and cortex. In the 4 tissues studied, the nucleus bound higher percentages of radioactivity, and more DHT was found in the nucleus than in the corresponding cytosol. In addition, conversion of T to DHT increased in parallel with the degree of binding. These two observations suggest that there is no qualitative difference in general handling of T by prostatic and neural ‘receptors’, although large quantitative differences are found.