Extraction of nuclear androgen receptors from rat prostate with different reagents

After in vitro labelling of androgen receptors in prostate tissue from castrated rats, about 70% of the labelled androgens in nuclei could be extracted with buffer solutions with 0.4 M KCl, or 10 mM pyridoxal phosphate, or 0.4 mM Cibacron blue, or heparin (0.2 mg/ml). In the nuclear extracts, 60-80% of the steroid was recovered as steroid-receptor complex. Sedimentation values of the receptors, on sucrose gradients containing 0.4 M KCl, were 3-4 S for the KCl extract and 4-5 S for pyridoxal phosphate and heparin extracts. The Cibacron blue extract contained an aggregated form of the receptor (5-7 S). The presence of the protease inhibitor di-isopropylfluorophosphate during isolation caused a small increase in S value of the receptors. However, the differences in sedimentation values between KCl, pyridoxal phosphate and heparin extracts remained. The receptors in the KCl extracts could be precipitated with protamine sulphate only after addition of 10 mM pyridoxal phosphate to the extracts. On the basis of these results it is concluded that the androgen receptors in rat prostate can be effectively extracted from nuclei by certain reagents which have in common a strongly negatively charged group and a less polar or hydrophobic region. These reagents form complexes with nuclear receptors and influence the sedimentation values and precipitability with protamine sulphate of these receptors.