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Biomedical subjects

V Hansson

Publications and source records attributed to V Hansson.

At least 199 records · Page 11Linked to original sources
PubMed1978

Androgens and androgen-binding protein in the rat epididymis.

The levels of testosterone, dihydrotestosterone (DHT), 5alpha-androstan-3alpha,17beta-diol and androgen-binding protein (ABP) were measured in various segments of the epididymis from adult rats which had been unilaterally orchidectomized for 4 weeks. On the 'intact' side, ABP concentrations were highest in the caput region. The segmental distribution of DHT closely followed that of ABP with the highest concentration in the caput (40 ng/g tissue) and lowest in the cauda (10 ng/g tissue) epididymidis. There was a high degree of correlation (r = 0.98) between the concentration of DHT in the epididymis and ABP levels. 'Castration' completely abolished the DHT gradient. The levels of testosterone and androstanediol were lower than those of DHT; most was present in the corpus epididymidis. The relative differences were reduced after 'castration'. It is concluded that ABP in the rat epididymis is the primary factor for determining the concentration of DHT in the epididymal fluid.

Androgens↗
PubMed1978

Age-related changes in responsiveness of rat Leydig cells to hCG.

The responsiveness of decapsulated testes and isolated Leydig cell preparations from rats (30-80 days of age) to a constant dose of 3 ng hCG/2 ml was assessed by comparison of the production of testosterone and "total 17beta-hydroxy androgen" (17beta-HA). When testosterone secretion was used as the index of response, there was a marked increase in the production with age by decapsulated testes and also by equal numbers of Leydig cells. When 17beta-HA was taken as the response parameter this increase was only marginal for the decapsulated testes and there was an age-dependent decrease when expressed per 10(6) cells. These differences probably reflect changes in the metabolism of testosterone to 5alpha-reduced products with increasing age because 80% of androgen secreted at 30 days is 3alpha-androstanediol and 86% is secreted as testosterone at 80 days. We conclude that for studies on hCG responsiveness and the steroidogenic capacity of immature rat Leydig cells (a) testosterone is an inappropriate response parameter and (b) this response undergoes a decrease rather than an increase during prepubertal development.

Aging↗
PubMed1978

Carnitine levels in human accessory sex organs.

Carnitine concentration was measured in human tissue obtained at surgery or autopsy. In all patients, the concentration of carnitine (nMol. g-1 tissue) was higher in epididymis than in testis, vas deferens, prostate, and seminal vesicles. There was no correlation between the tissue levels of testosterone in the testis and the concentration of carnitine in epididymis. As in the rat and baboon, carnitine is also found in high concentrations in the human epididymis.

Adolescent↗
PubMed1977

In vitro synthesis of rat testicular androgen-binding protein (ABP).

Testicular tissue from immature and adult rats shows in vitro synthesis of androgen-binding protein (ABP). The ABP synthesis is dependent on a complete tissue culture medium, the incubation temperature and the age of the rats. ABP synthesis is inhibited at 0 degrees C or in the presence of cycloheximide, puromycin or sodium fluoride. Immature (17-25-day-old rat) testes showed a higher rate of ABP synthesis per 100 mg tissue than adult rat testes during 'baseline' conditions (no additions to the medium). Addition of NIH-FSH-S10 or testosterone to the medium increases the production of ABP by the testicular minces. The in vitro techniques have proved to be useful for studies of direct hormonal influence on the Sertoli cell protein synthesis.

Aging↗
PubMed1977

hCG suppression of LH receptors and responsiveness of testicular tissue to hCG.

A single injection of 75 IU of human chorionic gonadotropin (hCG) into adult male rats caused a dramatic reduction in the concentration of membrane receptors for luteinizing hormone (LH) in the testis. The mean receptor level reached a nadir which was 5--10% of that in the control testes, 3 days after the injection, after which it gradually returned toward normal. This cannot be due to increased competition caused by the injected hCG since no decrease was observed at a time when the circulating levels of hCG were at a maximum (2--24 h after injection). Furthermore, at a time when receptor levels had been maximally reduced, circulating hCG was at or below the level of detection. Reduction in the number of LH binding sites in the testis was associated with a decreased responsiveness of the testicular tissue to hCG as measured by hCG-stimulated testosterone production in vitro. This inhibitory effect of large quantities of LH on its own receptor is suggested as a possible explantation for the previously observed low concentrations of LH receptor in the testis of the testicular feminized male (tfm) rat. This syndrome is characterized by high endogenous levels of plasma LH (Sherins et al., 1971).

Animals↗
PubMed1977

Androgen stimulation of prolactin receptors in rat prostate.

Specific receptors for iodine-labelled human prolactin ([125I]hPrl) are present in membrane preparations of the rat ventral prostate. The binding is saturable with an apparent association constant (Ka) of 2.2 X 10(9) M-1 and a binding capacity of about 1 pmol/100mg prostatic tissue. The binding of [125I]hPrl is inhibited by hPrl, ovine Prl (otprl) and human growth hormone, but not by ovine FSH or LH. Serum from rats having Prl-producing pituitary tumors caused a displacement of the [125I]hPrl from the receptors, and the displacement curve was parallel with that of the hPrl standard. Treatment of immature rats with varying doses of dihydrotestosterone propionate (10-5000 microng) causes a dose-dependent stimulation of Prl receptors calculated both as binding sites per mg of membrane protein and as binding sites per prostate. Androgen stimulation of prostatic Prl receptors increases the tissue sensitivity for circulating Prl and may be one reason for the known increases in endogenous cAMP levels in prostatic tissue after androgen treatment in vivo.

Animals↗
PubMed1977

Prolactin binding in rat testis: specific receptors in interstitial cells.

Specific receptors for [125I]hPrl (human prolactin) are present in membrane preparations of rat testis. The receptors are specific for lactogenic hormones (prolactin and human growth hormone) but do not bind gonadotropins. The prolactin receptors are localized exclusively in the interstitial cell tissue, and are not present in membrane preparations from isolated seminiferous tubules. The localization of prolactin receptors interstitial tissue suggests that the effect of prolactin on LH/hCG-stimulated testosterone production is due to a direct effect of prolactin of Leydig cells.

Animals↗
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↗