Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The two tryptophan residues in ovine and bovine prolactins were modified by reaction with 2-nitrophenylsulfenyl chloride in 75% formic acid. These derivatives exhibited an important loss of receptor affinity (less than 1% of the native hormones) to a rabbit mammary gland preparation. To a lesser degree, they also lost their binding affinity to specific guinea pig antibodies as detected by radioimmunoassay. The chemical modifications induced a change in the folding of the polypeptide chain, which in itself could be partly or totally responsible for the loss of biological or binding activities. This conformational change has been analyzed by circular dichroism and by prediction of secondary structures from the amino acid sequence using the method of Garnier et al. (Garnier, J., Osguthorpe, D.J. and Robson, B. (1978) J. Mol. Biol. 120, 97--120). The comparison of predicted prolactin and somatotropin structures revealed almost identical alpha-helix, turns and coil regions with an overall content of 67% alpha-helix, 5% beta-sheet, 17% turn and 11% of aperiodic structures. These values were close to those obtained from circular dichroism. The conformational change of the chemically modified hormones as compared to native folding, can be described as a partial loss of alpha-helical structure and an increase in beta-sheet content.
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PMID:Receptor binding and conformational properties of bovine and ovine prolactins after chemical modification of the two tryptophan residues. 22 37

7,12-Dimethylbenz[alpha]anthracene-induced rat mammary tumors were dissociated with collagenase and hyaluronidase and placed into primary culture. In most cultures, specific binding of 125I-labeled ovine prolactin was (i) lower than that for the original tumors unless bovine prolactin (1 microgram/ml) had been added to the dissociation medium, and (ii) varied with the type of growth medium used. The level of prolactin binding in cultured cells was relatively constant for the first 7-10 days. Prolactin binding in cultured cell homogenates was maximal at pH 7.0, proportional to cell protein, specific for prolactin, and reached a steady state by 12 h at 22 degrees C. The half-maximum inhibition of 125I-labeled prolactin binding by unlabeled prolactin was 100 ng/ml for cells grown in 5-1000 ng of prolactin/ml. After prolactin was removed from the growth medium, the level of available binding sites progressively increased, reached a maximum at 48 h and then declined. At 48 h, the dissociation constant for prolactin binding (Kd approximately 1 x 10(-10) M) was comparable to that in tumors. In some cultured tumors, a 48-h treatment with 0.5 or 1.0 ng of prolactin/ml caused an apparent increase in the level of prolactin binding. Prolactin increased DNA synthesis and its removal caused a reduction in [3H]estradiol and [3H]-R5020 binding to cultured cell cytosols.
Mol Cell Endocrinol 1979 Apr
PMID:Prolactin receptors in primary cultures of carcinogen-induced rat-mammary tumors. 22 41

Anterior pituitary glands were transplanted beneath the kidney capsule of intact, adult male rats to induce hyperprolactinaemia. This resulted in reduced serum levels of LH and FSH and increased adrenal weight. In pituitary-transplanted rats, testicular hCG-receptor binding was increased by 55 to 175%, whilst the capacity of the testis to secrete testosterone in vitro was greatly reduced. Injection of ovine LH into control and pituitary-transplanted rats resulted in similar percentage reductions in hCG-receptor binding in the two groups. This treatment impaired the in vitro steroidogenic responsiveness of testes from control rats at 24 h after injection, but had no major effect on the already-impaired, steroidogenic responsiveness of testes from pituitary-transplanted rats. Although induction of hyperprolactinaemia resulted in marked changes in Leydig cell function, these alterations were possibly due to the chronically reduced serum gonadotrophin levels in hyperprolactinaemic rats as well as a direct effect of prolactin on the Leydig cell.
Mol Cell Endocrinol 1979 Oct
PMID:The effect of induced hyperprolactinaemia on Leydig cell function and LH-induced loss of LH-receptors in the rat testis. 22 61

Orthodox views for the origin of the high concentration of prolactin (PRL) present in amniotic fluid suggest it is derived from maternal or fetal serum. However, the data on which these conclusions are based can also be interpreted to indicate that this hormone may be a product of placental or periplacental tissues. Trophoblast or amnion do not appear to produce PRL, while PRL synthesis by decidua-chorion is suggested from experiments in the rhesus monkey and by in vitro incubation of human tissue. Production of PRL by an extrapituitary cell is not without precedent and would be a simple explanation for high amniotic fluid PRL concentrations. Moreover, decidual-chorionic PRL would be strategically placed to mediate local functions of this hormone such as osmoregulation and myometrial inhibition.
Mol Cell Endocrinol 1978 Jun
PMID:Hypothesis: placental membranes produce prolactin. 35 8

A computing method for calculation of total similarity of two amino acid sequences depending on the number of gaps introduced into these sequences has been developed. It was based on Needleman--Wunsch--Sankoff's principles. The application of the method to randomized sequences enables us to select the optimal alignment of real sequences, in which the number of gaps is statistically justified. In this paper an example of the application of this approach is described and the statistically optimal alignment of somatotropin and prolactin amino acid sequences with two gaps is suggested.
Mol Biol (Mosk)
PMID:[Construction of optimal alignment of two amino acid sequences: a solution of the problem of unnecessary gaps]. 38

Estradiol is likely involved in stimulating developmental changes in the ability of the rat pituitary to secrete prolactin. To investigate the possibility that these changes involve proliferation of prolactin cells, estradiol effects on pituitary growth and prolactin synthesis were examined. Estradiol treatment of immature female rats stimulates increases in pituitary weight, [3H] thymidine incorporation, DNA content and prolactin synthesis. Treatment of rats with the DNA synthesis inhibitor, hydroxyurea, partially blocked the ability of estradiol to stimulate prolactin synthesis suggesting that at least part of the effect of estrogen is due to cell proliferation. These results suggest that estrogen-induced proliferation of prolactin cells is involved in the developmental processes of the pituitary.
Mol Cell Endocrinol 1979 Mar
PMID:Estrogen-induced prolactin and DNA synthesis in immature female rat pituitaries. 44 85

Treatment of female or male rats with estradiol benzoate led to an almost complete reversal of the inhibitory effect of low doses of dopamine on prolactin secretion. These data indicate that estrogens which have previously been shown to exert a potent antidopaminergic activity on prolactin secretion in anterior pituitary cells in primary culture have similar effects in vivo.
Mol Cell Endocrinol 1979 Jun
PMID:Antidopaminergic activity of estrogens on prolactin release at the pituitary level in vivo. 46 81

Estrogens stimulate prolactin (PRL) synthesis by GH3 cells, a clonal strain of rat pituitary cells grown in culture. At 4 degrees C the binding of [3H]17 beta-estradiol to monolayer cultures of GH3 cells was specific and of limited capacity, with half-maximal and maximal binding after 1--2 h and 12 h, respectively. Scatchard analysis showed one single class of binding sites with Kd = 3.1 X 10(-10) M and n = 309 X 10(-15) mol 17 beta-estradiol/mg cell protein, calculated to give approx. 25,000 binding sites per cell. At 4 degrees C less than 10% of the specifically bound [3H]17 beta-estradiol was found in the nuclear fraction. When the incubation temperature was raised to 37 degrees C, the amount of radioactivity in the nucleus increased to 25% within 30 min with a corresponding reduction in the cytoplasm. The cytosol fractions from monolayer cultures as well as from tumors of GH3 cells contained specific 17 beta-estradiol binding proteins, having a sedimentation constant close to 8S in a salt-free buffer and 4S in the presence of 0.5 M KCl. scatchard analysis showed one single class of binding sites with Kd = 3.6 X 10(-10) M and n = 258 X 10(-15) mol 17 beta-estradiol/mg cytosol protein (GH3 tumor tissue). Thus, GH3 cells grown in culture and in the intact animal have similar binding characteristics as judged from the data for binding affinity, capacity and specificity. After the in vivo administration of [3H]17 beta-estradiol to GH3 tumor-bearing rats, radioactivity could be extracted (0.5 M KCl) from purified nuclei bound to 4.5S macromolecules. We suggest that the action of 17 beta-estradiol on GH3 cells involves an initial binding of the steroid to specific receptors in the cytoplasm, followed by transport of a fraction of the hormone-receptor complexes to the nucleus involving a temperature-sensitive step.
Mol Cell Endocrinol 1978 Oct
PMID:Receptors for 17beta-estradiol in prolactin-secreting rat pituitary cells. 56 89

Thyroidectomy reduced the incorporation of [3H]amino acids into total rat pituitary proteins as well as into electrophoretic fractions corresponding to growth hormone (GH) and prolactin. A single injection of thyroxine (200 microgram/kg) reversed the effects of thyroidectomy on the GH (12 h) and prolactin (36 h) fractions. Evidence for a general increase in the rate of pituitary protein synthesis following this treatment was less conclusive, but two injections of the hormone had a definite stimulatory effect. [3H]Uridine uptake by the pituitary and its incorporation into RNA were elevated for 2 weeks after thyroidectomy. Thyroxine failed to suppress these changes for at least 36 h after injection. Actinomycin C (400 microgram/kg) inhibited pituitary RNA synthesis and blocked the stimulatory effect of thyroxine on amino acid incorporation into the GH fraction. These results indicate that thyroid hormones: (1) promote pituitary protein synthesis, probably as a consequence of their effects on somatotrophs and lactotrophs; (2) exert a stimulatory effect on GH synthesis by affecting transcription.
Mol Cell Endocrinol 1978 Apr
PMID:Thyroid hormone effects on protein and RNA metabolism in the rat anterior pituitary. 65 88

1. The effect of infusion of ovine prolactin was studied in anaesthetized dogs pretreated with bromocryptine to reduce the release of endogenous prolactin. 2. Prolactin, injected intravenously and also directly into one kidney, resulted in a 12--18% increase in glomerular filtration rate (GFR) by both kidneys. 3. This increased GFR was not associated with any demonstrable changes in whole-kidney blood flow, distribution of intrarenal blood flow, fractional excretion of sodium or osmolar or free-water clearance. 4. We conclude that ovine prolactin produced an increase in GFR not dependent on an increase in whole-kidney plasma flow.
Clin Sci Mol Med 1978 Oct
PMID:Effect of prolactin on glomerular filtration rate. 71 48


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