Localization of Prolactin Binding in Prostate and Testis: The Role of Serum Prolactin Concentration on the Testicular Lh Receptor

Aragona, Cesare; Bohnet, H. G.; Friesen, Henry G.

doi:10.1530/acta.0.0840402

Cited by 125 publications

(46 citation statements)

References 5 publications

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“…It has been shown, for instance, that inhibitory effects of induced hypoprolactinemia on LH bin ding can be recorded only beyond a certain age [1], and that PRL deficiency becomes associated with decreased serum androgen only at the age normally characterized by already high peripheral androgen [15]. In the present experiments naloxone-induced hypoprolactinemia was also associated to a fall of serum androgen, and this association also de pended on age and initial level of androgen in circulation.…”

Section: Discussionsupporting

confidence: 59%

“…In addition, three complementary types of experiments were designed to enable (1) estimates of the time course of naloxone-evoked serum androgen changes by means of repeated sampling in intrajugularly catheterized immature rats, (2) in vitro estimates of testicular stero idogenesis after in vivo naloxone administration, and (3) an evaluation of the possible direct effects of the opiate antag onist on testicular steroidogenesis, measured in vitro in the presence of various concentrations of naloxone.…”

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confidence: 99%

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Rapid Naloxone-Induced Alterations of Androgen Variables in the Growing Male Rat

et al. 1987

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Contrary to earlier views on the inability of naloxone to affect androgen variables by way of general circulation, systemically applied naloxone (2.5 mg/kg body weight, single i.p. or i.v injection) has been shown to rapidly induce (within an hour) a significant fall (–35,7% on the average) of the concentration of serum androgen (testosterone and dihydrotestosterone; (T + DHT) in peripubertal rats (51–58 days old). Such a response to the opiate antagonist was absent, however, in low-androgen prepubertal animals (37–44 days old) and in those among peripubertal rats which still showed subcritical initial levels of androgen in circulation (<1.5 ng/ml; experiments with repeated blood sampling in catheterized animals). In peripubertal rats naloxone was also shown to induce a significant decrease (–36%) in basal in vitro androgen production by testes removed 15 or 30 min following the intraperitoneal administration of the opiate antagonist. Such an inhibitory effect on basal steroidogenesis has not been observed in control multiple-dose experiments in which incubated testes from naloxone-naive rats have been directly challenged with naloxone: on the contrary, enhancing direct effects were recorded, but only with the highest concentration of naloxone tested (KM M). The possibility thus remains open that indirect inhibitory effects of injected naloxone may be operational in intact animals. Hypoprolactinemia, known to interfere in an age-dependent manner with the responsiveness of Leyding cells to luteinizing hormone (LH), may be of particular relevance: a significant fall of serum prolactin (PRL; -46%) has been regularly observed after systemic naloxone in those age groups which also responded to the opiate antagonist by a fall of circulating androgen and a decrease in basal in vitro steroidogenesis. A concomitant rise of serum LH has also been recorded after naloxone, but in all rats including the prepubertal group which did not respond with decreases of serum PRL and androgen.

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Section: Discussionsupporting

confidence: 59%

mentioning

confidence: 99%

Rapid Naloxone-Induced Alterations of Androgen Variables in the Growing Male Rat

et al. 1987

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“…A high concentration of prolactin can also disrupt the con¬ version of testosterone to its active metabolite 5-adihydrotestosterone (Katovich et al, 1985 Bartke, 1981;Takase et al, 1990), no effect in rams (Barenton and Pelletier, 1980) (Aragona et al, 1977), hamsters (Amador and Bartke, 1991) and pigs (this study) but not in rams (Barenton and Pelletier, 1980 …”

Section: Radioimmunoassaysmentioning

confidence: 62%

Effect of hypoprolactinaemia and hyperprolactinaemia on LH secretion, endocrine function of testes and structure of seminiferous tubules in boars

Jedlinska

Rozewiecka²,

Ziȩcik³

1995

Reproduction

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“…This is the first event in the biological action of PRL and other protein and polypeptide hormones on the target tissues. Membrane receptors for PRL have been demonstrated in mammary tumors in rats (9)(10)(11)(12) and in the normal and cancerous prostate of rat and man (13,14). Detection of receptors for hormones in a malignant tissue is of great value for determining its hormonal dependence and the course of future treatment.…”

Section: Introductionmentioning

confidence: 99%

Micromethod for the determination of free and total prolactin receptors: measurement of receptor levels in normal and malignant mammary and prostate tissues.

Ben-David¹,

Kádár²

1986

Proc. Natl. Acad. Sci. U.S.A.

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A sensitive micromethod for the determination of free and total prolactin receptors in normal or malignant tissues has been developed. Positive and negative quality controls are incorporated in the procedure. Either whole tissue or the pellet fraction remaining from tissue that had undergone processing for estrogen receptors can be used. Crude microsomal and plasma membrane fractions obtained by homogenization and differential centrifugation are incubated with labeled prolactin in the presence or absence of increasing amounts of unlabeled hormone. The labeled ligand is prepared by a stoichiometric iodination procedure in which one atom of iodine-125 is incorporated into one molecule of the hormone, resulting in an intact labeled prolactin with a high specific activity of 170-186 muCi/micrograms (1 Ci = 37 GBq). Human prolactin labeled by this procedure has much greater specific binding capacity to various rat tissues than does iodinated rat prolactin. This technique permits an accurate measurement of prolactin receptors in as little as 50 micrograms of membrane protein. Highest levels of free and total prolactin receptors were found in the liver of 60-day-old female rats that served as a positive control. Liver of immature 21-day-old male rats, devoid of prolactin receptors, was used as a negative control. The amount of detectable free receptors was dependent on the level of circulating plasma prolactin. In 3-day postpartum lactating rats with high prolactin levels in plasma, all prolactin receptors in the mammary glands were found to be occupied, and no free receptors could be detected. When these receptors were desaturated from the endogenous prolactin by exposure to 3 M MgCl2, one class of receptors in a high quantity (1.75 nmol/mg of protein) and with a moderate affinity (Kd = 6.41 X 10(-9) M) was detected. A similar type of receptor was found in the mammary glands of rats at midpregnancy and of cycling adult female rats. In malignant rat mammary tissue, however, fewer receptors (27 pmol/mg of protein) but with a very high affinity (Kd = 6.8 X 10(-14) M) were detected. Normal ventral and dorsolateral rat prostate contained two classes of prolactin receptors (Kd = 3.46 X 10(-10) M and 1.93 X 10(-8) M). In the cancerous rat prostate, however, only one of these two classes of receptors was detected, and the number was smaller.

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Localization of Prolactin Binding in Prostate and Testis: The Role of Serum Prolactin Concentration on the Testicular Lh Receptor

Cited by 125 publications

References 5 publications

Rapid Naloxone-Induced Alterations of Androgen Variables in the Growing Male Rat

Rapid Naloxone-Induced Alterations of Androgen Variables in the Growing Male Rat

Effect of hypoprolactinaemia and hyperprolactinaemia on LH secretion, endocrine function of testes and structure of seminiferous tubules in boars

Micromethod for the determination of free and total prolactin receptors: measurement of receptor levels in normal and malignant mammary and prostate tissues.

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