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Biomedical subjects

W Heyns

Publications and source records attributed to W Heyns.

At least 109 records · Page 6Linked to original sources
PubMed1978

Purification and characterisation of prostatic binding protein and its subunits.

The prostatic binding protein, previously described in rat ventral prostate, was isolated. The purified protein binds pregnenolone with an affinity of 1.2 X 10(6) M-1 and contains an average of 0.84 binding site per molecular. Its carbohydrate content is 3.2%. Its Mr, estimated by gel filtration, is 51 000 but in the presence of 6 M guanidine hydrochloride or 0.1% dodecylsulfate it dissociates into two subunits (S and F), which can be separated by polyacrylamide gel electrophoresis or by chromatography on hydroxyapatite. The Mr of these subunits is about 17 000, when estimated by gel filtration in 6 M guanidine hydrochloride, or 19 000 for subunit F and 20 000 for subunit S, when measured by dodecylsulfate/polyacrylamide gel electrophoresis. Their isoelectric points, estimated by isoelectric focusing in 8 M urea, are 4.6 for subunit F and 4.9 for subunit S. Prostatic binding protein and both subunits have a very similar amino acid composition. Upon reduction of disulfide bridges each subunit dissociates further into two components: one of these components is the same in both subunits.

Amino Acids↗
PubMed1978

Secretion of prostatic binding protein by rat ventral prostate: influence of age and androgen.

Rat ventral prostate of adult male rats contain a large amount of prostatic binding protein (PBP). Immunological evidence indicates that this protein is a specific secretion product of this gland. The amount and concentration of PBP in ventral prostate show marked changes as a function of age. PBP is low but detectable (0.009 and 0.002 U/mg prostate) in 5- and 10-day-old rats and increases thereafter in a biphasic way to adult levels (0.619 U/mg prostate). After castration of PBP drops to 0.054 U/mg prostate after 10 days and 0.030 U/mg prostate after 21 days. The concentration of PBP returns to precastration levels after 2 weeks of androgen treatment. Estradiol and progesterone are ineffective in this respect. The antiandrogen, cyproterone acetate, counteracts the stimulatory effect of testosterone propionate.

Aging↗
PubMed1977

Prostatic binding protein. A steriod-binding protein secreted by rat prostate.

Rat prostatic cytosol contains a high concentration of a prostatic binding protein with peculiar steroid-binding properties. Indeed, in spite of a relatively low affinity, charcoal adsorption can be used for its measurement. Furthermore, the binding is not specific for particular steroids and increases very strongly after delipidation. In delipidated cytosol the concentration of the binding site is 3.1 micronmol/g protein and the apparent affinity for pregenolone 1.7 X 10(6) M-1. The high concentration of prostatic binding protein in prostatic fluid shows that this substance is secreted by the prostate. Prostatic binding protein has the following physicochemical characteristics: it is precipitated by ammonium sulfate between 50 and 70% saturation; the elution position from a Sephadex G-100 column corresponds to a molecular weight of 51000; it sediments in sucrose density gradients at 3.7 S and is eluted from DEAE-cellulose columns at about 0.25 M KCl. On polyacrylamide gel electrophoresis the binding activity coincides with the major cytosolic protein band. This band has the same mobility as serum albumin in 7% gels, but a higher mobility in more concentrated gels.

Animals↗
PubMed1976

Interconversion between 17 beta-hydroxy-5alpha-androstan-3-one (5alpha-dihydrotestosterone) and 5alpha-androstane-3alpha, 17 beta-diol in rat kidney: heterogeneity of 3alpha-hydroxysteroid oxidoreductases.

3alpha-Hydroxysteroid oxidoreductases catalyzing the interconversion between 17 beta-hydroxy-5alpha-androstan-3-one (5alpha-dihydrotestosterone) and 5alpha-androstane-3alpha, 17 beta-diol (3alpha-androstanediol) have been studied in rat kidney. Three enzymes can be distinguished: a soluble NADPH-dependent oxidoreductase, a microsomal NADPH-dependent enzyme and a microsomal NADH-linked enzyme. Traces of the microsomal enzymes are consistently observed in the 108 000 X g supernatant. Studies on crude preparations reveal that these enzymes differ not only in subcellular localization and co-factor requirement, but also in optimum pH, kinetic characteristics, sensitivity to potential steroidal inhibitors and sensitivity to detergents, ionic strength and temperature. Moreover, salient sex differences exist in the activity of all three kidney enzymes. The soluble NADPH-dependent enzyme is more active in female rats whereas both microsomal enzymes are considerably more active in male animals. The microsomal NADH-dependent oxidoreductase displays favorable characteristics to catalyze the 3alpha-dehydrogenation of 3alpha-androstanediol. Evidence is presented that it is mainly this enzyme that enables the kidney to use 3alpha-androstanediol as an efficient precursor for the local formation of 5alpha-dihydrotestosterone.

Androstane-3,17-diol↗
PubMed1976

Secretion rates of LH and FSH during infusion of LH-FSH/RH in normal women and in patients with secondary amenorrhea: suggestive evidence for two pools of LH and FSH.

Normal women in the early follicular phase and in the luteal phase of the cycle, and patients with secondary amenorrhea received on consecutive days a rapid intravenous injection (50 mug) and a two or four-hour infusion (25 mug/h) of synthetic LH-FSH/RH. The responses of LH and FSH were evaluated by the measured plasma concentrations, as well as by the calculated pituitary secretion rates and by the amounts of hormone released. To estimate these pituitary secretion rates of LH and FSH, a simplified mathematical model is proposed. During an infusion of LH-FSH/RH the secretion rates of both LH and FSH increased in the three groups of women in a biphasic way with a dip after 1 to 2h of infusion, suggesting that besides the pool mobilized by a rapid intravenous injection of LH-FSH/RH there is a second pool of (stored) gonadotropins. For LH the increase above baseline concentrations was higher in group II (luteal phase) than in group I (follicular phase) or in group III (amenorrhea) and this both after a bolus injection and during infusion of LH-FSH/RH. For FSH a similar pattern of response prevailed during an infusion of LH-FSH/RH. After a bolus administration, however, the FSH release was relatively higher in group III (amenorrhea) than in both groups of normal women in which the increases were about the same. The latter finding suggests that the first pool of FSH is released by a different mechanism than the second pool.

Adult↗
PubMed1975

Ammonium sulfate precipitation as a tool for the study of androgen receptor proteins in rat prostate and mouse kidney.

Ammonium sulfate precipitation has been used for the separation of bound and free steroids in rat prostate and mouse kidney cytosol equilibrated with tritiated androgens. A high affinity, low capacity binding protein has been identified in the 35% saturation precipitate. Biochemical and physiological data indicate that this protein is identical with the previously described 8-10 S androgen receptor. It has been demonstrated that this receptor protein binds 17 beta - hydroxy-5alpha-androstan-3-one (DHT) and testosterone in both tissues. The apparent dissociation constant (Kd) of the prostatic receptor for DHT and of the renal receptor for testosterone is 1-2 nM. The number of binding sites equals 57 and 23 fmoles/mg protein in prostate and kidney respectively. Dterminations of apparent inhibition constants (Ki) for 26 steroidal and non-steroidal compounds suggest that the binding sites in these tissues is similar or identical.

Ammonium Sulfate↗