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Biomedical subjects

H Rui

Publications and source records attributed to H Rui.

At least 73 records · Page 4Linked to original sources
PubMed1987

Prolactin selectively stimulates ornithine decarboxylase in the lateral lobe of the rat prostate.

In androgenized-hypophysectomized rats, ovine prolactin stimulated the activity of the ornithine decarboxylase (ODC) of the lateral lobes, but not the ventral and dorsal lobes of the prostate glands in a time- and dose-dependent fashion. High degrees of enzyme stimulation were associated with significant elevations in the endogenous levels of its product, putrescine. The relative response to prolactin over basal activities was relatively unaffected by indomethacin but decreased with cycloheximide, suggesting that prostaglandins do not mediate the effects of the hormone, but that a high rate of protein synthesis is a prerequisite for its expression. Indomethacin alone significantly increased the basal activity of the enzyme above control levels, suggesting that prostaglandins may normally exert a degree of inhibition on the ODC. The selective activation of the lateral lobe ODC supports previous reports of a differential response of the various prostatic lobes to prolactin, and also provides a convenient biochemical response for examining details of prolactin action on this organ.

Androgens↗
PubMed1987

Independent control of citrate production and ornithine decarboxylase by prolactin in the lateral lobe of the rat prostate.

Prolactin stimulated the citric acid content of the lateral lobe of the prostate of androgenized-hypophysectomized rats in a time-dependent manner. This stimulation of citric acid levels was not blocked by pretreatment of the animals with the ornithine decarboxylase (ODC) inhibitor, alpha-difluoromethyl ornithine (DFMO), suggesting that the prolactin induction of citric acid in this organ is not mediated through activation of the ODC. The efficacy of the dose of inhibitor used was monitored by analysis of the diamine product of ODC, putrescine. Further evidence of an independent control of citric acid and polyamine synthesis in the lateral lobe was provided by their differing age distributions in intact animals. ODC activity decreased sharply with age, whereas the tissue concentrations of citric acid remained relatively constant. Both studies suggest that although citric acid and ODC are modulated by prolactin, their synthesis or activation are controlled independently of each other.

Aging↗
PubMed1987

Further observations on the autoregulation of the prolactin receptor in rat ventral prostate explants.

In confirmation and extension of an earlier preliminary communication, ovine prolactin was found to elevate prolactin binding by approximately 100% in rat ventral prostate explants incubated for 20 h in vitro. A stimulation was observed with low doses of ovine hormone (150 micrograms/l) which, from available data on the relative biological potencies, could be considered equivalent to the upper limit of the physiological range of endogenous rat prolactin. The response was associated with a lag period of 3-6 h. The effect could be obtained with other lactogenic hormones, including human and rat prolactin and human growth hormone, but not with non-lactogenic hormones such as insulin, hCG, corticosterone, testosterone or oestradiol. The prostaglandin synthesis inhibitor, indomethacin, and the Ca2+-antagonist, verapamil, could not counteract the increase in prolactin binding induced by prolactin treatment, nor could dibutyryl cyclic AMP alone mimic the response. These data suggest that prostaglandins, Ca2+ or cAMP do not mediate the alteration in receptor binding. Furthermore, inhibition of lysosome activity by chloroquine could not alone increase the prolactin binding in the control tissues, suggesting that up-regulation does not simply reflect a protective action of prolactin on receptor degradation.

Animals↗
PubMed1987

Thyrotrophin-releasing hormone in human ejaculate.

Immunoassayable TRH in human ejaculate was eluted from a gel column in a form with a molecular weight larger than that of the native peptide. With reverse-phase high-performance liquid chromatography (HPLC) the same activity co-eluted with standard TRH. Incubation of ejaculates at room temperature for 8 h was associated with a time-related increase in the total immunoassayable TRH. Analysis by HPLC of ejaculates after 12 h of incubation at room temperature indicated that, whereas the levels of the peptide co-eluting with native TRH declined with time, there was a concomitant increase in the concentration of a molecular species which also cross-reacted with the TRH antiserum, but which was more hydrophobic. The latter species is presumably identical to the tetrapeptide recently described by others and which may arise from the proteolytic degradation of secretory macromolecules. Although immunological activity was present in all six fractions of split ejaculates, the bulk of the peptide was associated with the later portions, implying a major vesicular contribution. However, secretions isolated from surgical preparations of the seminal vesicles contained undetectable levels of peptide, suggesting that the ejaculation process may represent a stimulus for its appearance in the semen. This study is further support for a local involvement of TRH in male reproductive function.

Chromatography, Gel↗
PubMed1986

Hormonal activation of the adenylyl cyclases of the rat and human prostate gland.

The rat ventral prostate and the human hyperplastic prostate contain adenylyl cyclases which can be activated by a variety of neurotransmittors, including vasoactive intestinal peptide (VIP), beta 2 adrenergic agonists, and dopamine. In both species the response to VIP was predominantly localized to the epithelial fraction. In the human tissue activation of the enzyme could also be achieved with prostaglandin E1 (PGE1) and an alpha 2 adrenergic agonist both associated with the stromal compartment. Castration in the rat caused a marked reduction in the basal activity of the enzyme and the maximal level of the hormone-stimulated response per cell (per mg DNA), but had only minor effects on the pattern of activation when expressed per mg membrane protein. Androgen treatment (dihydrotestosterone propionate, 2.5 mg/day) prevented the castration effects. Estrogen treatment (estradiol benzoate, 125 micrograms/day) could not prevent the castrational changes but maintained enzyme activity at a level above that of the castrate. There were no major qualitative differences in the pattern of activation of the cyclase between the different lobes of the rat prostate and the seminal vesicle.

Adenylyl Cyclases↗
PubMed1986

5 Alpha-reductase in the non-secretory cells of the rat ventral prostate epithelium.

Kinetic constants for the 5 alpha-reductase were determined in freshly isolated epithelial cells from the rat ventral prostate. Studies were also performed on stromal tissue but not isolated stromal cells for comparison. Secretory and non-secretory epithelial cells were separated by centrifugation in a Percoll gradient. Both epithelial cell populations metabolized testosterone to predominantly 5 alpha-dihydrotestosterone (5 alpha-DHT), although when expressed per cell the capacity for conversion was 3-4-fold higher for secretory cells (7.4 pmol/min/10(6) cells) than for non-secretory cells (2.3 pmol/min/10(6) cells; P less than 0.01 in 4 separate studies). When compared per mg cytosol protein this difference became non-significant. Stromal tissue contained a 5 alpha-reductase Vmax (expressed) per mg protein) which was comparable to the non-secretory cell enzyme. Lineweaver-Burke plots revealed different Km values for the different cell populations (12.5, 5.9 and 4.7 microM for secretory, non-secretory and stromal cells, respectively) suggesting the presence of different isoforms of the enzyme, or differences in the intracellular concentrations of enzyme antagonists.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1986

Homologous up-regulation of the prolactin receptor in rat prostatic explants.

Exposure of explants of rat ventral prostates and a rat Leydig cell tumour to ovine prolactin for 20 h caused alterations of the subsequent membrane binding of 125I-human prolactin to an extent and in a direction dependent on the dose of hormone used. Low prolactin concentrations (1-10 micrograms/2 ml) were associated with an increase in binding (up-regulation) which was 75% in the case of the prostatic tissue and 500% in the case of the tumour tissue above control levels. Higher concentrations caused a dose-dependent decrease in binding to below control levels (down-regulation), alterations which could not be explained by receptor occupancy. Time studies with an up-regulatory dose of hormone (3 micrograms/2 ml) indicated that the effects of prolactin on its receptor did not begin to become manifest until after 6-12 h of culture. The results suggest that homologous up-regulation of prolactin binding may be a general feature of prolactin target organs and that explant cultures of prostatic tissue may provide a convenient model for exploring its mechanisms.

Animals↗
PubMed1986

Time- and temperature-related alterations in seminal plasma constituents after ejaculation.

The effects of temperature and incubation time were examined on the concentrations of the following seminal plasma constituents in ejaculates from seven healthy volunteers: prostatic acid phosphate (PAP), citric acid, testosterone, prostaglandin E (PGE), fructose, protein, putrescine and the polyamines spermidine and spermine. The results indicated that the majority of glandular products were stable up to 3 h after ejaculation when stored at room temperature, with the exception of the prostatic diamine putrescine, which appeared to undergo rapid metabolism. Prolonged periods of incubation resulted in a gradual reduction in the levels of fructose and a significant increase in the activity of PAP and the levels of spermidine. On the basis of these findings it appears that an evaluation of the functional integrity of the accessory sex glands can be carried out on semen up to 3 h after ejaculation.

Acid Phosphatase↗
PubMed1986

Ejaculate composition after masturbation and coitus in the human male.

The levels of fructose, acid phosphatase, citric acid, zinc, maltase, testosterone, prostaglandin E, putrescine, spermidine and spermine were compared in ejaculates collected by masturbation and after coitus in the same individuals. Coitus was associated with a significantly larger semen volume and increased concentrations and total amounts of prostaglandin E and polyamines in the ejaculate. In contrast, the concentrations of the conventional glandular parameters remained relatively unaffected, although a slight dilution of the seminal vesicle contribution to the ejaculate occurred after coitus. In the majority of cases, ejaculates provided by masturbation were significantly enriched in spermatozoa, but the total contributions under both conditions remained the same. It is concluded that the assessment of semen quality in male individuals using the conventional parameters of accessory gland function can be made with ejaculates provided by masturbation or coitus.

Acid Phosphatase↗
PubMed1986

Short-term effects of mating on the accessory sex glands of the male rat.

Mating in the rat was associated with a significant reduction in the tissue concentrations of the presumptive secretory products of the male accessory sex glands: prostatein and the amines, putrescine, spermidine and spermine (ventral prostate lobe), zinc (lateral prostate lobe) and fructose (coagulating gland). The amount of secretory product discharged and the time taken to restore precopulatory levels differed for the different lobes. Within 12-24 h of the mating period, the activity of ornithine decarboxylase and cytosolic oestrogen binding in the ventral prostate lobe underwent a transient increase which lasted 2-3 days. No change was observed in prolactin binding. Circulating testosterone concentrations were significantly elevated above control values 12 h after the start of mating but were significantly lower than control values at 24 h. A gradual recovery to concentrations in controls occurred over the next 2-3 days. None of these changes could be explained by alterations in gonadotrophin or prolactin release.

Androgen-Binding Protein↗
PubMed1986

Biochemical correlates of asthenozoospermia: a lesion at the level of the sperm adenylyl cyclase.

Studies of the adenylyl cyclase in spermatozoa from 10 asthenozoospermic and 10 normal men revealed major differences with regard to the activation of the enzyme by various drugs and metal ions. While the response to acetate ions was normal, activation of the enzyme by forskolin and the GTP analogue [Gpp(NH)p] was uniformly impaired. In addition, in 4 of the patients the ratios of the Mn2+- and Mg2+-dependent activities of the enzyme were significantly higher than normal, suggesting a delay in the transformation of the enzymes catalytic unit from the soluble to the membrane-bound form. No differences could be recorded in a variety of seminal plasma components including prostatic acid phosphatase, citric acid, zinc, putrescine, spermidine, spermine, fructose, prostaglandin E, and testosterone. Furthermore, the DNA fluorescence patterns of the spermatozoa measured by flow cytometry were within the range of control variations, suggesting that chromatin condensation, and thus nuclear maturation, proceeded normally. The study suggests that a lesion in the adenylyl cyclase system of the germ cells may explain at least some of the motility disturbances seen in infertile males.

Acetates↗
PubMed1985

Circadian rhythms in accessory sex gland function in the male rat.

Alterations in various parameters of accessory sex gland function were monitored during two separate 24 h periods in adult male rats, and compared to fluctuations in the circulating levels of testosterone, prolactin, corticosterone and LH. Bimodal circadian rhythms in ventral prostate prolactin binding, cytosolic oestrogen binding and seminal vesicle weight could be discerned which appeared to be related to a similar rhythmicity in circulating testosterone levels, but with a phase shift of 3 h. Prostatic membrane bound adenylyl cyclase activities (basal and hormone stimulated) and prostatein concentrations followed different patterns possibly correlated to other endocrine changes.

Adenylyl Cyclases↗
PubMed1985

Short-term effects of prolactin on prostatic function in rats with lisuride-induced hypoprolactinaemia.

The effects of a single injection of ovine prolactin on prostatic function were monitored in intact, intact androgenized and castrated-androgenized rats rendered hypoprolactinaemic after 7 days of treatment with a potent dopamine agonist, lisuride. Hypoprolactinaemia was associated with reductions in ventral prostate weight, polyamine levels, lateral lobe zinc and the concentration of the ventral prostate protein prostatein, but an elevation in the level of cytosolic oestradiol binding. Whether these differences attained statistical significance depended on whether the animals were intact, intact-androgenized or castrated-androgenized. With the exception of ventral prostate weight and lateral lobe zinc concentrations, a single injection of prolactin restored or reversed these changes towards control levels within 12 h, which could not be explained by an indirect effect of the hormone on adrenal or testicular function. No effects of lisuride or prolactin were observed with regard to the content of fructose in the coagulating gland or in the degree of prolactin binding to prostatic membranes.

Androgen-Binding Protein↗
PubMed1985

Testicular and glandular contributions to the prolactin pool in human semen.

The immunoreactive prolactin in human seminal plasma originates predominantly from two sources, the seminal vesicles and the testicular-epididymal axis. The following evidence supported a testicular-epididymal origin: Vasectomy reduced the content of prolactin in the ejaculates by 50%; the concentration of seminal prolactin was highly correlated (r = 0.54, p less than 0.003) with the concentration of sperm in a normal population of young and middle-aged men; and prolactin concentrations in the split ejaculates of normospermic men revealed a profile that corresponded to the sperm distribution pattern. Evidence supporting an additional contribution from the seminal vesicles included the following. The split ejaculate of an azoospermic individual coincided more with the distribution of the vesicular parameter fructose; vasectomy did not cause the disappearance of prolactin from the ejaculate; and split-ejaculate analyses weakened the possibility of a major prostatic source.

Acid Phosphatase↗
PubMed1985

Estrogen receptors in stromal and epithelial fractions of the ventral prostate of rats.

The cytosol from rat ventral prostates contains two estrogen-binding components that can be separated in a glycerol gradient: a high-affinity (KD = 4.2 X 10(-10) M), low-capacity (110 fmole/mg DNA) species that runs in the 8S region of the gradient, and a lower-affinity (KD = 2.4 X 10(-9) M), higher-capacity (410 fmole/mg DNA) 4S protein. Separation of prostate tissue into stromal- and epithelial-enriched fractions was associated with the disappearance of the latter component. When compared per milligram DNA stromal- and epithelial-enriched fractions contained similar amounts of the high-affinity 8S-binding protein. In vivo estrogen treatment caused a time-related disappearance of the protein from the intact cytosol presumably as a result of translocation. No major differences in the degree of binding to the high-affinity component were observed in rats of different ages. Estrogens seem to exert direct effects on both stromal and epithelial tissues of the prostate.

Aging↗
PubMed1984

Prolactin desensitizes the prostaglandin E1-dependent adenylyl cyclase in the rat prostate gland.

Prior exposure of the rat ventral prostate to a high dose of ovine prolactin in vivo or in vitro caused the specific desensitization of the prostaglandin E1-dependent adenylyl cyclase. Maximal desensitization was achieved in vivo 6 h after exposure to 100 micrograms prolactin and complete resensitization occurred after 7 days. No heterologous desensitization of the response of the cyclase to other hormones tested was observed. Incubation of isolated secretory cells with prolactin and prostaglandin E1 desensitized the subsequent response to the same prostaglandin. Simultaneous exposure of the cells to indomethacin prevented the prolactin-induced effect. Prolactin could also induce similar changes in the prostaglandin E1-dependent cyclase of rat Leydig cell tumour cells in vivo, suggesting that this may represent a phenomenon shared by other prolactin target organs. This study supports the hypothesis that prostaglandins may constitute second messengers for prolactin effects on the prostate gland.

Adenylyl Cyclases↗
PubMed1984

Seminal plasma characteristics during frequent ejaculation.

Seven young men provided a semen sample every 8 h for 2 days. Citric acid, zinc, acid phosphatase , spermine, fructose and protein were measured in the samples. Despite a dramatic reduction in semen volume, the concentration of the majority of the parameters remained constant during the period of study. The protein profile of the ejaculates, as assessed by 2-dimensional electrophoresis, also did not change. Levels of citric acid, zinc and acid phosphatase were closely correlated, while spermine, which is also believed to be of prostatic origin, showed no correlation with these other parameters. The spermine concentration of the ejaculates increased significantly during the period of high ejaculation frequency and returned to normal levels after a 3 day abstinence period. In view of the fact that spermine accumulation in tissues appears to be associated with growth and protein synthesis this increase in seminal spermine may reflect a stimulation of prostatic cell activity.

Acid Phosphatase↗