[Study on the translocation of cytosolic dihydrotestosterone-androgen binding protein complex to the nuclei in rat submandibular gland].

The low molecular weight inhibitor (LMWI) and the translocation of dihydrotestosterone (DHT)-androgen binding protein (ABP) complex of the cytosol to the nuclei in rat submandibular gland (SMG) was studied by dialysis, ultrafiltration and glycerol linear gradient centrifugation procedures. Prebound cytosol was obtained by the incubation with 3H-DHT at 4 degrees C for 3hr in the presence or absence of 100 fold excess of unlabeled DHT prior to contact to nuclei. When prebound cytosol was dialyzed or ultrafiltrated, the binding ability of 3H-DHT-ABP complex to nuclei was increased up to 3 times of the control (nontreated prebound cytosol). The sedimentation rate of 3H-DHT-ABP complex by glycerol linear gradient centrifugation was 4S for dialyzed or ultrafiltrated prebound cytosol and 8S for control. These transformation of 8S to 4S and activation to the nuclear binding of 3H-DHT-ABP complex by dialysis or ultrafiltration were inhibited by molybdate in the prebound medium. The similar transformation of 8S to 4S and activation to the nuclear binding of 3H-DHT-ABP complex was shown in heated prebound cytosol. These results indicate that the LMWI regulate activation of 3H-DHT-ABP complex. The molecular weight of the dialyzed LMWI were estimated as 7,000 by dialysis or ultrafiltration membrane and SDS-PAGE. From the in vitro two step binding assay, it was revealed that rat SMG contained the low molecular weight protein (M. W. 7,000) in cytosol having a inhibitory effect on the translocation to the nuclei of 3H-DHT-ABP complex.