Dihydrotestosterone-binding Protein Research Articles

Testicular androgen binding protein in zinc deficient rats

Zinc deficiency in rats and humans is characterized by an increase in serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and decrease in serum testosterone level and spermatogenesis. The possibility that an abnormality in the androgen binding protein may be responsible for decreased spermatogenesis in zinc deficiency was investigated. White male rats weighing approximately 220 gm were allotted to three groups: zinc-deficiency (Zn-D), Pair-fed (PF), and Ad-libitum fed controls (Ad-Lib). Androgen binding protein (ABP), total protein, testosterone, and dihydrotestosterone (DHT) were assayed in testicular cytosol by established techniques. Testosterone, DHT, and DHT binding protein sites per pair of testes were reduced in Zn-D in comparison to PF and Ad-Lib controls (p<.02). The results were not significantly different when expressed in terms of per mg of protein. Serum testosterone and DHT, testicular weights, and zinc in tibia and testes were decreased in Zn-D animals in comparison to both controls (p<.02). In conclusion our studies show that androgen protein binding sites and steroidogenesis were not affected by zinc deficiency, rather the major effect was on testicular growth. Inasmuch as zinc is known to play an important role in DNA and protein synthesis, zinc deficiency may affect adversely cell division and restrict testicular growth.

Androphilic proteins in the human prostate.

Dihydrotestosterone-binding protein in cytosols from human prostates was different from the R1881- and R5020-binding proteins. The R1881- and R5020-binding proteins in the cytosol were very similar and most of the binding sites for R1881 were capable of binding R5020. However, nuclear extracts showed equal binding to dihydrotestosterone and R1881, but not to R5020, suggesting that there might not be a progestin receptor in the human prostate. Maximum binding sites to dihydrotestosterone, R1881, and R5020 in cytosols were very similar among "normal" and pathological prostates except that dihydrotestosterone binding was higher in "normal" prostates than in the pathological ones. Histochemically, R1881-binding was observed in the epithelial cells and in malignant cells, but not in the stroma.

Progestin-binding protein in human benign prostatic hypertrophy.

Cytosols from human benign prostatic hypertrophy contained progestin-binding components which bound to R 5020, ORG 2058 and progesterone in high affinity fashion. Most of the protein bound to R 5020 was recovered in the precipitate with 0-30% saturation of ammonium sulfate. The R 5020-binding protein showed sedimentation coefficients of 3.6S and 8.4S, and was eluted in the void volume of a Sephadex G-200 column. This protein was clearly distinguished from the dihydrotestosterone-binding protein by its precipitability by ammonium sulfate, heat stability and susceptibility to delipidization. R 5020 and ORG 2058 binding were markedly inhibited by the addition of R 1881, therefore, most of the binding to progestin in cytosols from the benign prostatic hypertrophy seems to be also the sites for R 1881. Although nuclear extract by 0.4 M KCl showed R 1881 binding, the extract did not contain the R 5020-binding protein, and this suggested that the progestin-binding protein observed in the cytosols does not seem to be the steroid receptor.

The presence of binding proteins for retinoic acid and dihydrotestosterone in murine and human colon tumors.

Retinoic acid-binding protein (RABP), which is distinctly present in embryonic colon and lung, is below the limits of detection in adult mouse colon and lung. The binding protein is present in malignant murine colon tumors as well as in lungs of animals bearing subcutaneously implanted tumors. Primary cell cultures from 1 g of colon tumor 26 gave rise to about 10(7) tumor cells and yielded 30 mg of extractable protein. The lower limit for detection of RABP, based on the appearance of its specific 2S peak after sucrose density gradient sedimentation, was 0.1 mg of protein, which corresponds to 3.3 x 10(4) tumor cells. After subcutaneous implantation of colon tumor 26 in mice, no RABP peak was evident in the lung extracts up to the fourth day. From the fifth day onwards, RABP appeared in lung extracts, possibly as a consequence of pulmonary metastasis. Fragments of mouse lungs containing the metastatic tumor foci were reimplanted subcutaneously and produced tumors that contained RABP at levels comparable to those in colon tumor 26. The primary subcutaneous tumors and pulmonary metastatic tumors showed the same histologic appearance--an undifferentiated carcinoma. On the 15th day of subcutaneous implantation of colon tumor 26 in mice, RABP was detected in lung and brain but in none of the other tissues where the protein is normally undetectable. After intraperitoneal implantation of colon tumor 26 in mice, no well-defined RABP peaks were detected from their liver extracts. None of the three normal human colon extracts analyzed for RABP or a dihydrotestosterone-binding protein (DHTBP) contained any detectable amounts of either of the binding proteins. However, 70% of the human colon tumors contained RABP and 90% contained DHTBP. Both of these binding proteins were evident in the two human colon tissues adjoining colon tumors.

Binding to R 1881 (methyltrienolone) of proteins from human benign prostatic hypertrophy.

Cytosol of human benign prostatic hypertrophy bound to R 1881 in a high affinity manner. Most of the protein which bound to R 1881 was recovered in the precipitate of a 0-30% saturation of ammonium sulfate, and was eluted in the void volume on a Sephadex G-200 column. The binding of cytosol to R 1881 was more inhibited by progestins than by dihydrotestosterone and estradiol-17 beta. The binder therefore seemed to be different from dihydrotestosterone-binding protein. The R 1881-binding component extracted from the nuclei by 0.4M KCl bound also to dihydrotestosterone in a high affinity manner. Cytosol prelabeled with R 1881 was bound to the nuclei in a nonsaturable process, and the extraction pattern of R 1881 by 0.4M KCl from the nuclei was almost identical to that in the case of dihydrotestosterone as the ligand. These results suggested that a part of the cytosolic protein which bound to R 1881 entered the nuclei where it bound to nuclear such components as dihydrotestosterone-binding protein.

Rat Adrenal Androgen Receptor: A Possible Mediator of Androgen-Induced Decrease in Rat Adrenal Weight

Many previous studies have demonstrated effects of gonadal steroids on adrenal weight in the rat. Most of these effects are indirect, depending upon alterations in the pituitary-adrenal axis for their expression. In this study we have attempted to examine the direct effects of gonadal steroids on adrenal weight in the rat. This was done using hypophysectomized, castrated male rats receiving ACTH replacement, a model which excludes pituitary-adrenal feedback effects. Estradiol-treated rats did not differ from controls, whereas testosterone-treated rats exhibited a small but statistically significant decrease in adrenal weight. As a first step in exploring the mechanism of this androgen effect, we have identified a specific dihydrotestosterone-binding protein in the rat adrenal gland. A single class of high affinity (Kd = 0.6-2.0 x 10(-8) M), saturable (28 fmol/mg cytosol protein), cytoplasmic binding sites was found using both protamine sulfate precipitation and dextran-coated charcoal assays. The specificity, sedimentation coefficient on sucrose gradient, and sensitivity to sulfhydryl reagents and heat of this dihydrotestosterone-binding protein are typical of the cytoplasmic androgen receptor from other androgen target tissues such as prostrate. We conclude that testosterone can decrease rat adrenal weight directly, and that the mechanism may involve a high affinity binding protein, as has been shown in other androgen-responsive systems.

Dihydrotestosterone-binding protein in cytosols of normal and hypertrophic human prostates, and influence of estrogens and anti-androgens on the binding.

Dihydrotestosterone-binding protein was observed in cytosols of the normal and hypertrophic human prostates. Association constant for dihydrotestosterone of cytosol of the normal prostate differed slightly from that of the hypertrophic prostate. However, maximum binding capacity was almost identical in these tissues. No distinct correlation was detected between proportion of glandular constituent and binding characteristics (Ka and maximum binding capacity) in the hypertrophic prostates. Influence of some steroids on the binding with dihydrotesterone was examined. Testosterone, estradiol-17beta, estriol, cyproterone acetate and SK & F 7690 inhibited the binding competitively. However, Sch 13521 did not exhibit any influence on the binding.