The formation of unconjugated and sulfoconjugated estrogens by Leydig cells of the boar testis.

The metabolism of radioactive androstenedione (A) and estrone (E1) was examined in preparations of enzyme-dispersed cells from testicular interstitial tissue of the boar. Incubations were made with two-cell populations from a discontinuous density gradient (10-90% Percoll). Products were separated into unconjugated and "conjugated" (water-soluble) fractions by countercurrent distribution (CCD) using an ether-water partition. As much as 75% of A and 20-25% of E1 appeared in the aqueous phase. Unconjugated and solvolyzed steroids were separated similarly into neutral and phenolic fractions by CCD with a system of toluene - 1 N NaOH. Radioactivity was found to be approximately equal in the two phases for each CCD. Partition chromatography on Celite columns for unconjugated and sulfoconjugated estrogens showed the presence of E1, estradiol, estrone sulfate, and estradiol sulfate from both radioactive substrates. Further identification of the estrogens was obtained from high performance liquid chromatography. The study included radioimmunoassays for estrogens in the media of cell preparations incubated without radiolabelled substrates. The results are in accord with the known high level of estrogen secretion by the testes of the mature male domestic pig and support the view of steroid sulfate secretion by the Leydig cells.