Extraction of nuclear androgen receptors by sodium molybdate from normal rat prostates and prostatic tumors

Abstract

Because sodium molybdate stabilizes steroid receptors, this compound has been included in the homogenizing medium in order to maximize the recovery of measurable steroid receptors in normal and neoplastic tissues. This study demonstrates that sodium molybdate extracts additional androgen receptors from prostatic nuclei in a concentration-dependent manner. Nuclei previously washed with Triton X-100 to remove the outer nuclear membranes released similar numbers of androgen receptors with sodium molybdate as the unwashed nuclei, suggesting that the extracted nuclear androgen receptors are associated with intranuclear matrices. Sucrose density gradient analyses revealed that sodium molybdate-extractable nuclear androgen receptors sedimented similarly to the 0.4 M KCl extract as 4S receptor complexes under high-salt conditions. We have compared the amount of nuclear androgen receptors extracted from normal prostates (ventral prostate and dorsolateral prostate) and Noble hooded rat and Dunning prostatic tumors by a sensitive translocation-extraction procedure. This procedure involves the incubation of minced prostatic tissues, isolated from castrated rats, with [3H]R1881 ( [3H]methyltrienolone; [6,7-3H]-17 beta-hydroxy-17 alpha-methylestra-4,9,11-trien-3-one) at 37 degrees for 2 hr. Crude nuclear pellets were prepared from the minced tissues, and nuclear androgen receptors were extracted with 40 mM Na2MoO4 or 0.4 M KCl. Results showed that the amount of nuclear androgen receptors present in the prostatic tumor nuclei is lower than that found in the normal. Although the percentage of nuclear androgen receptors extracted by sodium molybdate or KCl is similar between androgen-dependent and androgen-independent prostatic tumors, the absolute amounts of nuclear androgen receptors per mg DNA extracted from the former are 2- to 8-fold higher than those found in the latter.