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PubMed1975

[Ultrastructure of the prolactin cells of the pituitary gland of female rats after stimulation with norethisterone enanthate].

Prolactine cells of rat anterior pituitary gland were studied with the electron microscope in thin sections and freeze-etch replicas after treatment with norethisterone-oenanthate. A pathological secretory process is caused in this cell type in rats, when treated with this compound. Prolactine cells grow in number and volume of single cells. This is especially due to an enormous proliferation of the Golgi apparatus. In the same time, however, exocytosis of hormonal secretory granules is apparently reduced. Therefore, serum hormone level remains nearly normal.

Animals↗
PubMed1977

Prolactin binding in ovariectomy-responsive and ovariectomy-nonresponsive rat mammary carcinoma.

Growth of the transplantable mammary tumor, MTW9, in W/Fu rats is greatly enhanced by elevated serum prolactin concentrations. This report compares the prolactin binding to tumor membranes in two mammary tumor strains derived from MTW9. Maximum binding to membranes of both tumors occurred at pH 7.6 after incubation for 30 hr at 4 degrees. The binding was inhibited only by polypeptide hormones that possess lactogenic activity. MTW9-P, an ovariectomy-responsive tumor developed in rats maintained on daily perphenazine injections, had 4-fold-higher prolactin binding than had MTW9MtT, an ovariectomy-nonresponsive tumor developed in rats bearing the mammosomatotropic pituitary tumor, MtTW10. Withdrawal of perphenazine from rats bearing MTW9-P caused a fall to normal of plasma prolactin, no tumor regression, and no significant change in prolactin binding. In contrast, resection of MtT resulted in tumor regression, a fall to normal of serum prolactin, and a nearly 3-fold increase in prolactin binding. Scatchard plots of prolactin binding data yield an apparent affinity constant, Ka, of 1.2 X 109 liters/mole for both tumors. The 4-fold-higher prolactin binding in the ovariectomy responsive variant suggests a positive correlation between ovariectomy response and the number of membrane prolactin-binding sites. No correlation between prolactin sensitivity and prolacting binding is apparent.

Animals↗
PubMed1977

Prolactin binding to R3230AC mammary carcinoma and liver in hormone-treated and diabetic rats.

Specific 125I-labeled prolactin binding was measured in membrane particles prepared from R3230AC mammary carcinoma and liver of tumor-bearing Fischer rats after either prolactin, estrogen, or lergotrile mesylate treatment, or after the induction of diabetes by streptozotocin. Hormone binding to tumors was decreased by treatment with prolactin (0.5 or 1 mg/day) or estradiol valerate (7.5 mg/kg/week). In contrast, prolactin treatment did not affect prolactin binding to liver membrane particles, but estradiol valerate treatment resulted in a four-fold increase in prolactin binding to this tissue. Lergotrile mesylate, which lowers plasma prolactin levels, did not affect tumor growth or prolactin binding to either tumor or liver. Prolactin binding to both tumor and liver was significantly reduced in diabetic rats, suggesting that insulin may play an important role in controlling tissue sensitivity to prolactin. Specific binding of 125I-labeled prolactin to enzymatically dissociated cells from R3230AC tumors was demonstrated in vitro. The binding capacity of the cells was found to be of the same order of magnitude as the binding capacity in membrane preparations when appropriate corrections were applied for yields of cells and membranes. R3230AC tumor, which is responsive to prolactin appears therefore to be a useful model system for further study aimed at elucidation of growth and metabolic response to the hormone prolactin in breast cancer.

Acetonitriles↗
PubMed1977

[Antigonadotropic actions of prolactin. Study of 10 cases of women with hyperprolactinemia].

In order to determine the pituitary or ovarian site of the anti-gonadotrophic action of prolactin (PRL), ten women with hyperprolactinaemia were studied in the following way: 1) Repeated estimations of PRL, gonadotrophins (LH and FSH), plasma estradiol and progesterone during six weeks of treatment with bromocriptine. 2) Verification of the effects of estradiol benzoate on LH and FSH levels before and after normalisation of prolactin. 3) Exploration of the ovarian response to the administration of human menopausal gonadotrophin. Without it being possible to exclude any direct effect of prolactin on the ovary, it may be affirmed that the hormone decreases the sensitivity of the gonadotrophic cells to the positive feedback mechanism exerted by plasma estradiol.

Adult↗
PubMed1977

[The effect of several sexual steroids, 2-bromo-ergokryptin and lisurid-hydrogenmaleate an the postpartum concentration of serum prolactin and lactation (author's transl)].

The effect of Ablacton, Estrovis 4000, 2 Brom-alpha-ergokryptin (Cb 154) and of Lisurid-hydrogenmaleate (LHM) on lactation and the serum concentration of prolactin postpartum was studied. 10 normal nursing postpartum patients served as control. LHM was tested in a double blind study compared to placebo. The serum prolactin (PRL) was determined daily for the first 10 postpartum days by radioimmunoassay. Inhibition of lactation was consistent with Cb 154 (89% of the cases). Within two to three days after the onset of treatment with Cb 154 the changes of pregnancy in the breasts had completely subsided. The sexual steroids resulted in inhibition of lactation in 60% of the postpartum patients but mastodynia continued. LHM showed no difference from group taking placebo. The serum prolactin levels postpartum remained as high as a nursing mother's or rose with the administration of steroids. The administration of Cb 154 resulted in a drop of the serum prolactin to non-pregnant levels with in 2 days. The serum prolactin levels under treatment with LHM were not different from the group slowly. In nursing mothers, the stimulus of suckling maintain the pituitary secretion of prolactin as showed by higher serum prolactin levels and a slower decreased to normals than in the non-nursing mothers.

Bromocriptine↗
PubMed1979

Inherent ranges of seminal prolactin in pre- and postvasectomy subjects.

Seminal immunoreactive prolactin (i prolactin) was studied in 14 healthy subjects, ages 31 +/- 2 SEM, before and after undergoing elective vassectomy for birth control. Seminal plasma was separated within 2 hours of ejaculation, and prolactin was measured in duplicate by radioimmunoassay. The difference between the prevasectomy (mean +/- SEM 11.1 +/- 0.8 ng/ml) and postvasectomy seminal i prolactin (mean +/- 9.9 +/- 0.7 ng/ml) was statistically significant (mean +/- SEM 1.21 +/- 0.53 ng/ml, paired t-test, t = 2.36, P < 0.05). The mean prevasectomy seminal prolactin correlated with the corresponding mean postvasectomy value of the same subject (linear regression analyses, r = 0.77, P < 0.001). This study suggested that the accessory sex organs were the major source of seminal immunoreactive prolactin, and that a minor contribution might come from the in vivo presence of spermatozoa and/or testicular secretions. It also suggested that the magnitude of seminal immunoreactive prolactin was characteristic for each individual.

Adult↗
PubMed1975

Clinics in endocrinology and metabolism. Investigative procedures.

In patients with hypogonadism, the exact cause of the deficient androgenisation is not always clinically apparent. The data presented demonstrate that by means of hormone measurements, basally or after stimulation tests, the exact level of the lesion can usually be determined. This allows a decision with regard to appropriate therapy to be made on the basis of an accurate diagnosis. In many instances basal measurements of pituitary and gonadal hormones are all that is required to decide the level of the lesion. Care in interpreting basal levels is required, however, in view of methodological limitations and of known physiological variations with age, time of day and hour-to-hour fluctuations. If the basal hormone levels are borderline, or if the 'reserve function' of part or all of the hypothalamic-pituitary-gonadal axis needs to be assessed, than the appropriate stimulation test should be performed. The indication for these stimulation procedures and results obtained in different conditions are described and problems of interpretation discussed.

Adult↗
PubMed1975

[The pulsatile LH fluctuation (spiking) dependent on the circulating prolactin. Studies during physiological (puerperium), functional pathological and TRH induced hyperprolactinemia].

The magnitude and frequency of episodic LH-fluctuations have been observed to change during the different phases of the menstrual cycle. A hypothalamic control center appears to be responsible for these variations. Disturbances of the hypothalamus often make themselves known through a lack of LH-episodes. Ahypothalamic derangement in women with functional amenorrhoea can result in a disregulation of gonadotropins as well as prolactin, thereby leading to hyperprolactinemia. One finds an inverse relationship between high prolactin secretion and cessation of or decreased pulsatile LH-secretion (spiking). LH-spiking was tested in physiological post partum, functional pathological and TRH-induced hyperprolactinemias. No LH-episodes were observed post partum after the end of HCG clearance although prolactin had returned to normal levels at 12 days p.p. The mode of LH-secretion in a group of functionally amenorrhoic patients was changed by a TRH-induced prolactin increase: the previously observed LH-spikes in these women could no longer be seen. Normal cycling women, however, were not affected. In patients with hyperprolactinemic anovulatory syndromes, prolactin suppressed LH-fluctuations reappeared after administration of 2-Bromo-alpha-ergocryptin. The inhibitory influence of hyperprolactinemia on the function of the gonadostat will be discussed. High plasma prolactin levels influence the cyclic and tonic hypothalamic function. Furthermore, prolactin appears to have a peripheral inhibitory influence on ovarian gonadotropin stimulation. Post partum anovulation and amenorrhoea can be caused by an antigonadotropic and antigonadic effect of prolactin.

Amenorrhea↗
PubMed1975

[TRH stimulation as an attempt at demonstration of the induction and involution of prolactin-secreting pituitary cells in pregnancy and puerperium and in pathological hyperprolactinemia].

The present paper discusses the relationship between functional hypertrophia or hyperplasia of the prolactin secreting cells in the pituitary and actual pituitary prolactin reserves in pregnant and post partum women. 35 randomly selected post partum patients from the 3rd to 12th day p.p. and 14 women in their 11th to 14th weeks of pregnancy volunteered to undergo a standard TRH-test. The control group consisted of 60 normoprolactinemic patients. Eleven pathologically hyperprolactinemic patients were compared to the normoprolactinemic and physiologically hyperprolactinemic groups. In all cases, plasma prolactin showed a linear decrease from the 3rd to 12th days post partum. The TRH induced increase became correspondingly greater as the basal prolactin levels decreased, i.e. an inverse relationship between these two parameters was seen. The TRH-induced increase was also always greater than the increase caused by suckling. A connection between prolactin and parity was not found. The inverse relationship between basal prolactin levels and the actual reserves which could be released by TRH stimulation can be explained in that there are two regulatory systems for prolactin. The estrogens stimulate basal prolactin and inhibit prolactin reserves. The actual prolactin reserve is, on the one hand, directly dependent on the degree of endogenous neurohormonal stimulation and, on the other hand, indirectly dependent on the endogenous estrogens through a feedback mechanism. The TRH-stimulation test is not suitable for determining a functional hypertrophia or hyperplasia of lactotropic pituitary cells.

Estrogens↗
PubMed1976

Prolactin binding to mammary gland, 7,12-dimethylbenz(a)-anthracene-induced mammary tumors, and liver in rats.

Specific binding of radioactively labeled prolactin was determined in membrane preparations from mammary glands and livers of rats during pregnancy and lactation. Prolactin binding to mammary gland increased throughout late pregnancy and early lactation, reached a maximum on Day 11 of lactation, and then declined. Maximum prolactin binding to liver membrane preparations was observed during late pregnancy and declined throughout lactation. Estradiol benzoate (20 mug/day), administered on Days 5 to 10 of lactation, reduced prolactin binding to mammary gland by 55%, increased binding to liver 2-fold, and reduced litter weight gain by 25%. Prolactin binding to 7,12-dimethylbenz(a)anthracene-induced mammary tumors was 3 times higher than that observed in lactating mammary gland. Administration of prolactin enhanced tumor growth but decreased specific prolactin binding to tumors. Lergotrile mesylate inhibited and estradiol benzoate (2 mug/day) enhanced tumor growth, but neither treatment affected prolactin binding to tumor membrane preparations. In contrast, higher doses of estradiol benzoate (20 mug/day) inhibited tumor growth and reduced prolactin binding. Prolactin binding varied widely within all groups of mammary tumors and was not clearly related to growth response or to altered circulating estrogen and/or prolactin levels. Hormone dependence in this animal tumor model is complex and may not be predicted on the basis of prolactin-binding capacity alone.

9,10-Dimethyl-1,2-benzanthracene↗