Characteristics of the rat prostate androgen receptors analyzed by sucrose density gradient and high-performance liquid chromatofocusing

Rat prostate cytosolic androgen-receptor complexes were analyzed by sucrose density gradient (SDG) centrifugation and by high-performance liquid chromatofocusing (HPCF). Without protecting agents, these complexes were resolved by HPCF at basic (8.25–7.1), intermediary (7.0–5.0) and acidic (4.6–4.2) pH. Sodium molybdate stabilized labeled complexes which migrated in the 8–9S and 3.5–6S areas on SDG. These were further stabilized by the presence of sodium molybdate and four protease inhibitors: complexes then sedimented mainly in the 8–9S area with a shoulder at 6–7S. Forms eluting at acidic pH on HPCF were favored by the presence of sodium molybdate and further enhanced by the addition of inhibitors, to the detriment of basic ones. Furthermore, when chromatographed on phosphocellulose (P-c), unretained complexes sedimented as a symmetrical peak on SDG centrifugation in the 8–9S area, but were eluted from HPCF columns as two entities at pH 4.1 and 4.6. The P-c retained complexes subsequently detached by 0.6 M KC1, were resolved into three entities by HPCF with a major component at pH 8.2, which sedimented in the 4S areas. These results demonstrate that the gradual decrease in the negative net charge of androgen receptor correlates with the gradual reduction in mass of the androgen-receptor complex. Moreover, this can be interpreted as further evidence for a heterogeneity of androgen receptor population in rat prostate, suggesting the involvement of a multistep mechanism preceding the induction of specific gene transcription by the hormone.