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Biomedical subjects

S C Weddington

Publications and source records attributed to S C Weddington.

At least 19 recordsLinked to original sources
PubMed1977

Effect of testosterone propionate on levels of carnitine and testicular androgen binding protein (ABP) in rat epididymis.

Twenty-one day old rats were treated for 10 days with various doses of testosterone propionate (TP) (10 micrograms to 10 mg/day) and the levels of L-carnitine and testicular androgen binding protein (ABP) were measured in the 105,000 x g supernatant fractions of epididymis. Treatment with TP in increasing doses had a biphasic effect on the level of ABP in the epididymis; thus, with doses of TP of 10-100 micrograms/day, the ABP level was reduced in a dose-dependent way, whereas with higher doses of TP (0.2 to 1 mg/day) the extent of reduction of ABP levels was less as the dose of TP increased. Treatment with high doses (5 mg or 10 mg/day) did not change the ABP level compared with non-treated control rats. The concentration of carnitine increased linearly (log dose-response) with increasing doses of TP (10-200 micrograms/day) and there was no further increase after treatment with higher doses of TP. In adult rats TP (175 micrograms and 17.5 mg/day) reduced the level of ABP but not the level of carnitine in the epididymis. These studies suggest, therefore, that ABP is of minor importance for the supply of androgens to the carnitine-concentrating cells in the corpus and cauda epididymis.

Androgen-Binding Protein↗
PubMed1976

Secretion and role of androgen-binding proteins in the testis and epididymis.

The Sertoli cell appears to be a target cell for both FSH and androgen. FSH stimulates the Sertoli cell to produce an androgen-binding protein (ABP) which may serve to increase the accumulation of androgen in the seminiferous tubular epithelium and make it available for binding by intracellular androgen receptors. This might be one way by which FSH enhances the action of androgen on spermatogenesis. Androgen acts on the Sertoli cell to increase its response to FSH resulting in increased production of ABP and of other substances which exert trophic effects on spermatogenesis.

Androgens↗
PubMed1976

Androgen receptors in male sex tissues of rats and humans.

A brief description of physicochemical properties of the androgen receptors in the various target tissues is given. It is suggested that androgen receptors in all organs and species are very similar if not identical. It is also suggested that apparent differences in steroid binding are not due to differences in steroid specificity of receptors, but rather due to organ specific differences in target tissue metabolism. A short discussion of our studies on androgen receptors in the prostate, epididymis and testis of human being is also included. The properties of these receptors are similar, if not identical to those described in rats, and we have not been able to demonstrate differences in androgen receptors of non-neoplastic and neoplastic tissue. From studies on testosterone metabolism it is demonstrated that human prostate is metabolizing testosterone to DHT much faster than the seminal vesicles. Furthermore, there is a drastic reduction in DHT formation in tissue from prostatic cancer compared to normal and hyperplastic prostatic tissue.

Androstane-3,17-diol↗
PubMed1975

Testicular androgen binding protein (ABP) - a parameter of Sertoli cell secretory function.

Using ABP as an index of Sertoli cell secretory function, several important features of the Sertoli cell have emerged: 1. The stimulation of ABP production by FSH clearly points to the Sertoli cell as a target cell for FSH (3,4,9-16,21,24). 2. The dramatic effects of androgens on ABP production both in immature and mature rats also suggest that the Sertoli cell is a target cell for androgen (3,12,14,16,25). 3. The striking reduction in ABP production in the cryptorchid testis raises the question whether impairment of Sertoli cell function is the primary reason for the loss of germ cells that occurs in this condition (20). 4. Drugs like nitrofurazone or ethionine, or X-irradiation only slightly affect the secretory function of the Sertoli cells (ABP production), indicating that these treatments most probably have direct effects on the germ cells as well. Thus, measurement of ABP production rate is a very important tool in order to evaluate how hormones, drugs and physical injuries might affect the secretory function of the Sertoli cell. This test system might be of great use in order to study the physiology and hormonal regulation of the Sertoli cells. It might also be valuable in pharmacological and toxicological studies.

Age Factors↗
PubMed1975

Purification and characterization of rabbit testicular androgen binding protein (ABP).

Testicular androgen binding protein (ABP) was purified from the epididymis of 1500 adult rabbits by the sequential use of ammonium sulphate precipitation, ion exchange chromatography on DEAE cellulose, gel filtration on Sephadex G-200, hydroxyl-apatite chromatography and preparative polyacrylamide gel electrophoresis. This procedure yielded a 1000-fold increase in specific activity compared to that of the 1500,000 x g supernatant, and the recovery of active ABP was about 3-5%. ABP is acid glycoprotein with a molecular weight of 65-68,000 daltons. Antisera to rabbit ABP raised in quinea pigs inhibit 3H-DHT binding to ABP as measured by SS-PAGE. When diluted rabbit serum containing TeBG is treated with the same dilutions of these antisera, identical binding inhibition curves are found. Thus, ABP and TeBG in rabbits appear to possess identical immunological determinants.

Amino Acids↗
PubMed1975

Testicular androgen-binding protein (ABP): comparison of ABP in rabbit testis and epididymis with a similar androgen-binding protein (TeBG) in rabbit serum.

Testicular androgen-binding proteins (ABP) in rabbit testis, caput epididymis and efferent duct fluid (EDF) were compared to a similar androgen-binding protein TeBg) in rabbit serum. The affinity of these proteins for 5alpha-dihydrotesterone (DHT) at 0 degrees C (KaABP = 1.6 X 10(9) M-1 and KaTeBG = 1.9 X 10(9) M-1) and their steroid specificities were similar (DHT greater than androstanediol greater than progesterone and androstenedione). ABP and TeBG had also almost identical Stokes radii (42.8 +/- 1.2 and 43.9 +- 0.8 A, respectively), sedimentation coefficients (4.7 +/- 0.2 S and 4.4 +/- 0.2 S, respectively) and electrophoretic mobility (Rf = 0.4 in 6 1/2% polyacrylamide gels). Calculation of molecular weights from Stokes radii and sedimentation rates indicated a molecular weight of 74,000 (69,000-78,000) for TeBG and 76,000 (71,000-82,000) for ABP. The corresponding frictional ratios were 1.61 for TeBG and 1.55 for ABP assuming a partial specific volume (v) of 0.70 cm3/g. Polyacrylamide gel electrophoresis (PAGE) at different gel concentrations gave a mean molecular radius of 2.74 nm, also indicating a molecular weight of about 75,000 (v = 0.70 cm3/g. ABP and TeBG could not be separated by PAGE; however, partial separation of ABP and TeBG was achieved by isoelectric focusing and ion-exchange chromatography on DEAE-cellulose. TeBG focused at pH 5.4, whereas ABP formed a distinct peak of bound radioactivity at pH 4.7. Also by ionexchange chromatography, ABP in both testis and epididymal supernatants was shown to have an apparently higher surface charge than TeBG in rabbit serum. The concentration of ABP in efferent duct fluid (2 X 10(-7) M = 60 pmol/mg protien) was much higher than TeBG in male rabbit serum (5.2 X 10(-8) M = 0.7 pmol/mg protein). These findings ruled against the possibility that ABP in the testis and epididymis could have been derived directly from serum. It is concluded that ABP and TeBG are very similar if not identical proteins both serving as transport and carrier proteins in their respective compartments.

Androstenedione↗
PubMed1975

FSH stimulation of testicular androgen binding protein (ABP): comparison of ABP response and ovarian augmentation.

Production of testicular androgen binding protein (ABP), ceases following hypophysectomy and can be stimulated by FSH. Within 24 h after the administration of FSH, ABP can be measured in caput epididymis supernatant and by 4 days after FSH treatment, the concentration of ABP reaches a plateau. In a 3-day assay, ABP production in immature hypophysectomized rats was stimulated by 31 mug NIH-FSH-P1 per day (0.08 U NIH-FSH-P1 per 3 days) which is comparable to the sensitivity of the ovarian weight augmentation test in hypophysectomized rats. The relative ovarian weight augmenting and ABP stimulating activities of various FSH preparations were in agreement, suggesting that the biological stimulus of the ABP response is, in fact, FSH. The ABP response to FSH could become a useful testicular bioassay for FSH. Such an assay would be more practicle if ABP could be measured by a radioimmunoassay.

Animals↗
PubMed1975

Regulation of seminiferous tubular function by FSH and androgen.

Seminiferous tubules contain a cytoplasmic androgen receptor similar to the receptors in the epididymis and ventral prostate. The presence of a cytoplasmic receptor indicates that androgens maintain spermatogenesis by a direct action on certain types of cells within the seminiferous tubule. The Sertoli cell appears to be one of the cell types containing androgen receptors and the receptor might also be present in spermatogonia, primary spermatocytes, or peritubular cells. The Sertoli cell is stimulated by FSH to produce an androgen-binding protein which may serve to increase the accumulation of androgen in the seminiferous epithelium and make it available for binding by intracellular androgen receptors. This may be a way in which FSH enhances the action of androgen on spermatogenesis. Androgens act on the Sertoli cell to increase its response to FSH. This action of androgens on the Sertoli cell results in increased production of androgen-binding protein and may enhance the production of other substances which exert trophic effects on spermatogenesis.

Androgens↗