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Biomedical subjects

V Hansson

Publications and source records attributed to V Hansson.

At least 235 records · Page 13Linked to original sources
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

Androgen-binding proteins in rat epididymis: properties of a cytoplasmic receptor for androgen similar to the androgen receptor in ventral prostate and different from androgen-binding protein (ABP).

The cytoplasmic recptor (CR) in rat epididymal 105,000 g supernatant was separated from the androgen-binding protein (ABP) by gel electrophoresis following labeling with [1,2,6,7-3H]-testosterone in vivo. ABP disappeared from epididymal supernatants after castration of hypophysectomy, while CR remained unchanged. CR was evenly distributed between caput and cauda, while much more ABP was present in caput. Properties of CR in epididymis and prostate were similar and distinctly different from ABP. Binding to CR was destroyed by charcoal treatment (1 mg/mg protein) of supernatant for 0 degrees C for 6 h, heating at 50 degrees C for 30 min, or exposure to the sulfhydryl blocking reagent, p-chloromercuriphenylsulfonate (1mM) at 25 degrees C for 30 min, while binding to ABP was unaffected. The isoelectric pH of CR (5.8) was higher than that of ABP (4.6). Dissociation of radioactive 5alpha-dihydrotestosterone (DHT) from CR and nuclear receptors was extremely slow (half-time at 0 degrees C is greater than 2 days), while dissociation from ABP was rapid (half-time at 0 degrees C is similar to 6 min). Cyproterone acetate (250 mg/100 g body weight) inhibited binding to CR both in epididymis and ventral prostate but did not affect binding to ABP. Nuclear uptake was inhibited by cyproterone to the same extent as binding to CR, indicating that nuclear uptake and binding are dependent on CR and independent of ABP. The time-course of uptake and binding in epididymal supernatant and nuclear fractions was essentially the same 1 day after bilateral castration when both CR and ABP were present or 8 days after castration when CR alone was present. It is concluded that the cytoplasmic receptor for androgen in rat epididymis has properties very similar to the androgen receptor in ventral prostate but different from ABP.

Androstenedione↗
PubMed1975

Androgen-dependent accumulation of carnitine by rat epididymis after injection of [3H]butyrobetaine in vivo.

After i.m. injection of [3H]butyrobetaine into rats, the accumulation of carnitine into the epididymis, prostate gland, seminal vesicles, testis and heart was studied. The concentration of radiolabeled carnitine into the cauda epididymis increased linearly with time up to 72 h after the injection of the precursor, while its level in the prostate and seminal vesicles decreased rapidly. Very low levels of carnitine were found in the testis. Castration reduced the carnitine accumulation by cauda epididymis to 6% of the control levels while treatment of castrated animals with testosterone propionate (500 mug/day) partly restored the carnitine uptake. Similar treatment with 17beta-oestradiol valerate or 17alpha-hydroxyprogesterone had no effect. Surprisingly, cyproterone acetate (5 mg/day) also significantly stimulated carnitine accumulation by the epididymis to a level above that of the castrated controls. Simultaneous injection of both cyproterone acetate and testosterone propionate to castrated animals caused an additive effect of these steroids. This indicated that cyproterone acetate in this system is working as a weak androgen. Treatment of rats with 17beta-oestradiol valerate also reduced carnitine accumulation by the cauda epididymis. This is due to suppression of pituiatry gonadotrophin secretion, since concommitant treatment with testosterone propionate (500 mug/day) caused a normalization of the carnitine uptake. Treatment of intact rats with cyproterone acetate significantly reduced the epididymal weight, but not the carnitine accumulation. 17alpha-Hydroxyprogesterone treatment had no effect either on the epididymal weight or the accumulation of the carnitine. Unilateral orchiectomy reduced the carnitine accumulation by the cauda epididymis to about 40% of that occurring in the non-operated control side. This indicates that the luminal contact between the testis and epididymis or the luminal content of the epididymis itself is of importance for the androgen-dependent metabolic process occurring in the cauda epididymis. Castration or hormone treatment did not change the conversion of butyrobetaine to carnitine, or the carnitine uptake by heart. Carnitine uptake by the testis after [3H]butyrobetaine injection was rather low and this would exclude the possibility of synthesis of carnitine in the testis as a source of epididymal carnitine. Carnitine only accumulated in the cauda epididymis in vivo 4 to 96 h after injection of [3H]butyrobetaine. The presence of radioactively labeled butyrobetaine or methylcholine was not detected.

Animals↗
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

Characterization of the androgen receptor in the anterior pituitary of the rat.

The specific androgen receptors for testosterone (T) and 5alpha-dihydrotestosterone (DHT) in the cytosol fraction of the anterior pituitary of rats have been further characterized using electrophoresis and isoelectric focusing in polyacrylamide gels. After labeling of the cytosol fraction in vivo and in vitro, we were able to demonstrate androgen-protein complexes moving with an electrophoretic mobility (Rf) of 0.5 in 3.25% acrylamide gels containing 0.5% agarose and 10% glycerol. This method was used for quantitative measurements of pituitary androgen receptors, allowing multiple samples to be run simultaneously with little or no non-specific binding. There was no measurable dissociation of the androgen-receptor complexes during electrophoresis. When radioactive testosterone (1 nM) was added to pituitary cytosol fractions in vitro, there was an increase in the binding up to 4 hours of incubation at 0 C and little or no increase between 4 and 24 hours. All the binding studies therefore were done by incubation overnight at 0 C. When cytosol fractions were incubated with increasing concentrations of radioactive testosterone, a typical saturation curve was found. Scatchard plot analysis showed a binding capacity of 12.0 femtomoles/mg protein and the equilibrium constant of dissociation was estimated to be 3.4 +/- 0.7 (SD) X 10(-10)M. Like other androgen-receptor complexes, the testosterone-receptor complex in the anterior pituitary gland had an extremely slow rate of dissociation at 0 C (t1/2 greater than 4 days). The steroid specificity of the cytoplasmic androgen receptors was tested in vitro by the competing efficiency of different unlabeled steroids for [3H] testosterone binding. T and DHT caused the same inhibition of [3H]T to the receptors. However, since metabolism, of DHT to 5alpha-androstane-3alpha,17beta-diol occurred even at 0 C, the affinity of DHT for the receptor is probably somewhat underestimated. Cyproterone acetate had approximately half the affinity for the receptor compared with T, whereas lower affinities were found for progesterone and 17beta-estradiol. Cortisol did not appear to have any affinity for the receptors. Isoelectric focusing in polyacrylamide gels showed a peak of bound radioactivity with an isoelectric point of 5.8. Thus, the characteristics of the cytoplasmic androgen receptors of the anterior pituitary gland are very similar to those of the androgen receptors described in the ventral prostate, epididymis, and testis.

Androgens↗
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↗