[Studies of progestin specific binding protein in the human prostate. [III]; Sodium molybdate effect on SDG analysis]

The effect of sodium molybdate on the specific binding protein (SBP) of synthetic progestin 17 alpha-methyl-[3H]-promegestone (R5020) in the cytosol of the human prostate was studied. In a sucrose density gradient analysis, two R5020 SBP components at 4S and 7-8S were observed. It was apparent that the 4S component was reduced and the 7-8S component increased with the addition of 10mM sodium molybdate into the cytosol. Therefore, the molybdate enhancement degree on total SBP amount (4S plus 7-8S) was decided by the relationship between the decreasing rate at 4S and the increasing one at 7-8S. It was shown that the molybdate effect was time-dependent and was not related to the SBP state, whether it was bounded with steroid or not. Moreover, it was estimated that the molybdate effect was not related to phosphatase inhibition since R5020 SBP in SDG was not enhanced by the addition of sodium fluoride which was a phosphatase inhibitor. In this report, the possibility of the existence of the 7-8S forming factor in the human prostate and the relationship between it and sodium molybdate was also discussed through an experiment on a Sephadex G-25.