1984 Volume 75 Issue 1 Pages 96-103
Recently, R1881 receptor assays in prostatic cytosol have been developed as a one point assay because of small amount of available tissues. However, further investigations were needed for their technical accuracies. We have reported that total tissue DHT levels of prostate might be a useful indicator to predict the androgen dependency of prostatic cancer as well as receptor assays, although relations in DHT levels and NBS of R1881 receptor have not been examined. Therefore, we investigated these correlations in total tissue, cytosol and nuclear extract of BPH and normal prostate.
Cytosols and nuclear extracts were incubated with 0.25-8.0nM of 3H-R1881 (6 points) for 20 hours at 4°C, then unbound steroids were removed by 0.5% dextran coated charcoal. Specific binding was defined as the difference between total binding and nonspecific binding which was not displaced by the addition of 100 fold excess cold R1881. Binding studies were performed in the form of Scatchard plot analysis. DHT levels were measured by the radioimmunoassay reported previously.
DHT levels of total tissue were correlated well with those of cytosol and nuclear extract (r=0.582, 0.647 respectively). Furthermore, they were also correlated with NBS of nuclear extract (r=0.575) but not with NBS of cytosol. This problem should be attributed to that cytosolic R1881 receptor was not a pure androgen receptor because it contained progesterone binding protein. It was considered that cytosolic R1881 receptor assay should not be an appropriate method to determine the androgen dependency of prostatic tissues.
R1881 receptor of nuclear extract which was prepared with high ionic solution (TEDGK buffer) was proved to be a 3-4S receptor by sephacryl S-200 gel chromatography and steroid specificity studies revealed that nuclear receptor was not inhibited by progestins. Since close correlations were noted between DHT levels and NBS of R1881 receptor especially in nuclear extract (r=0.776), it was considered that the determination of total tissue DHT levels might possess clinical usefulness to clarify the androgen dependency of prostatic cancer. In addition, it has some merits, since it requries minimum amount of tissue and is stable for temperature compared to receptor assays.
