Metabolites of testosterone in the brain of the newborn female rat after an injection of tritiated testosterone

Hypothalamic, septal, amygdaloid and cortical areas from brains and the pituitaries of 5-day-old female rats were analyzed for their content of labeled dihydrotestosterone (DHT), androstenedione (A), 5α-androstan-3β-17β-diol (3β-Adiol), 5α-androstan-3α-17β-diol (3αaAdiol), estradiol-17β (E₂) and estrone (E1) 10, 15 and 30 min after an intraperitoneal injection of 20 μCi testosterone-7-³H (T). Two experiments were carried out. In both, tissues were pooled from 10 rats and the steroids quantified by the double isotope dilution technique. Tritiated T₂ A and DHT were identified in all parts of the brain studied. Together they accounted for 11.5–28.0% of the radioactivity extractable by organic solvents at 10 min and 5.5–11.3% of the radioactivity extractable at 30 min. The amount of DHT at 10 min was 1.5–3.7% of the radioactivity and fell to 0.9–2.5% by 30 min. Specimens from the different brain areas had to be combined to provide sufficient labeled 3αAdiol for positive identification. The radioactivity associated with 3βAdiol was insufficient to establish radiochemical homogeneity. Ei was present in identifiable amounts in the hypothalamic and combined septal and amygdaloid specimens but not in those specimens from the cortex or the pituitary. In the hypothalamus E₂ accounted for 0.31% of the total radioactivity and for about 0.11% of the radioactivity in the combined amygdaloid and septal specimens. The number of counts associated with the E2 standard did not exceed the background. The ratios of the different steroids to each other varied in the different areas studied; however, there were no consistent differences in the pattern of metabolites in the different areas.