Estramustine binding in rat, baboon and human prostate measured by high pressure liquid chromatography

High pressure liquid chromatography (HPLC) was used to determine 3H-estramustine (estradiol-17β3N-bis-[2-chlorethyl] carbamate), 3H-17β-hydroxy-5α-androstan-3-one ( 3H-dihydrotestosterone or 3H-DHT), 3H-estradiol-17β ( 3H-E 2) and 3H-3β-hydroxy-5-pregnen-20-one ( 3H-pregnenolone) binding in 50μ1 of cytosol utilizing a column which separates proteins in the molecular weight range of 2,000 to 70,000 daltons. The rat prostate contains a protein in considerable concentration and with the highest affinity for estramustine (375,000dpm 3H-estramustine per mg. cytosol protein) among the substances tested. Operationally, we have named this protein “estramustine binding protein” (EBP), though it is very likely similar to other previously described prostatic proteins (e.g., α-protein, prostatein, prostatic binding protein). The sensitivity of the HPLC method disclosed EBP-like proteins, but in much lesser concentrations, in some of the other tissues tested. The concentration of these proteins in the human and baboon prostates was much lower (average for the baboon cranial lobe 4800dpm/mg cytosol protein, with a somewhat higher value for the caudal lobe) than that in the rat gland. The amount of the EBP-like protein was higher in prostatic cancer than in that of benign prostatic hypertrophy (BPH) (range 9350 – 25,900 vs. 2200 – 18,900 dpm/mg cytosol protein). In the human, the highest value was found in one normal prostate tested (106,000dpm/mg cytosol protein).