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Introduction Prolactin (Prl) has been reported to play a role in reproduction, in particular ovarian function, and lactation in many mammalian species (for reviews, see Sinha 1995 , Freeman et al. 2000 ). However, it was not
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SUMMARY
The prolactin concentration in the dog pituitary gland was determined by isoelectric focusing of adenohypophysial extract in polyacrylamide gels followed by densitometry of the isolated stained hormone band. Dogs of both sexes and various ages (excluding newborn pups and weanlings) were studied. The bitches comprised animals at different stages of the oestrous cycle and also included a small number of pregnant, lactating or ovariectomized animals.
Low pituitary prolactin concentrations were found in males, sexually immature females and dioestrous females. Concentrations about 1·5 times as high occurred in oestrous, metoestrous (luteal) and ovariectomized females. Post-partum lactating bitches had the highest pituitary prolactin concentrations, these being double those occurring at dioestrus. With the exception of relatively high concentrations in ovariectomized bitches, these results are in good agreement with findings in the rat, mouse and rabbit. The persistence of high pituitary prolactin levels throughout metoestrus was believed to be associated with differences between the canine and murine reproductive cycle. Age did not influence pituitary prolactin levels in either males or females.
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thyrotrophs but also of prolactin (PRL) from lactotrophs, and in some species also of growth hormone (GH) from somatotrophs ( Galas et al . 2009 ). The availability of radiolabeled TRH, and later of its more stable analog 3Me-His-TRH, facilitated the
Departmenté Nutrição Aplicada, Instituto de Nutrição, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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Departmenté Nutrição Aplicada, Instituto de Nutrição, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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Departmenté Nutrição Aplicada, Instituto de Nutrição, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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Departmenté Nutrição Aplicada, Instituto de Nutrição, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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Departmenté Nutrição Aplicada, Instituto de Nutrição, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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and changes in their macronutrient, iodine, and thyroid hormone content ( Passos et al. 2000 , 2001 a , Passos et al. b ). Previously, we reported that the milk production suppression through the inhibition of prolactin (PRL) synthesis with
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Semen samples were collected from 35 men and the levels of prolactin in semen and seminal plasma were measured. There was no significant difference in prolactin concentrations between the two fluids (t = 0·333, P > 0·7). There was also no correlation between the prolactin concentration and the kinematic viscosity of the semen (r = 0·065, P > 0·7).
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ABSTRACT
There is evidence that prolactin (PRL) influences gastrointestinal function. However, the sites at which prolactin exerts these effects are not known. A monoclonal antibody was therefore generated against the rabbit mammary gland prolactin receptor (MAb 218) and used to study the distribution of the prolactin receptor in the rabbit gastrointestinal tract (GIT) by immunohistochemistry. MAb 218 is an IgG 1 κprecipitating antibody which precipitates major affinity cross-linked mammary gland prolactin receptor subunits of molecular masses 45 and 80 kDa. It has an affinity of 0·8 × 109 mol/l for the prolactin receptor and does not react with GH or insulin receptors in precipitation assays. MAb 218 immunoreactivity was observed in classical prolactin target cells such as mammary gland epithelium, and this immunoreactivity was abolished by preincubation of MAb 218 with purified prolactin receptor but not by preincubation with purified GH receptor.
In the GIT, the most intense immunoreactivity was associated with the oesophageal epithelium, chief (zymogenic) cells of the fundic mucosa, pancreatic islets of Langerhans and surface epithelial cells of the duodenum and jejunum. Other specific elements of the GIT were immunoreactive at lower levels or were immunonegative. No immunoreactivity was observed in these locations with a control monoclonal antibody (MAb 50·8) of identical isotype to 218.
To support the immunohistochemical findings, rabbit gastric mucosal membranes were used to show the presence of lactogen-specific binding. Scatchard analysis of 125I-labelled human GH binding to the gastric mucosal membranes with rat prolactin as displacing ligand yielded an affinity constant (K a) of 1·0 ± 0·2 × 109 mol/l with a capacity of 3·5 ± 0·4 fmol/mg protein. Affinity cross-linking and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the gastric receptor revealed lactogenic hormone-binding subunits of molecular masses 43, 68 and 83 kDa. The 68 kDa subunit was not seen in rabbit mammary gland or ovarian tissue, and may be unique to gastric mucosa.
In conclusion, we have demonstrated the presence of a high affinity lactogenic receptor in specific epithelial cell subpopulations of the GIT. This localization of the prolactin receptor in the GIT will assist in further functional assignment of prolactin to gastrointestinal physiology.
Journal of Endocrinology (1993) 139, 371–382
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assayed in duplicate. The lower detection limit for prolactin using this kit is about 0.6 ng/mL. The intra-assay coefficients of variation of the assay were found to be 3.85–5.32%. Estrogen ELISA assay Plasma estrogen levels were measured using rat
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ABSTRACT
The interaction between prolactin and zinc was examined in vitro in the human prostate gland. The results indicated that prolactin did not modulate the acute uptake of zinc into benign prostatic hypertrophy tissue whereas zinc, in contrast, increased the uptake of prolactin into the prostate gland. Our study further showed that the augmented uptake of prolactin by zinc was partly due to an increase in the non-specific binding properties of the peptide hormone. We were also able to demonstrate that the specific binding of 125I-labelled human prolactin to the receptor was reduced in the presence of zinc by a competitive mechanism.
J. Endocr. (1984) 102, 73–76
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Radioimmunoassay techniques have revealed very high levels of prolactin in the range 1·2–10 μg/ml in samples of human amniotic fluid (AF) during the 10th-20th weeks of pregnancy and also a gradual increase in the level of prolactin in the maternal blood serum throughout pregnancy (Hwang, Guyda & Friesen, 1971; Friesen, Hwang, Guyda, Tolis, Tyson & Myers, 1972; Tyson, Hwang, Guyda & Friesen, 1972). Between the 10th and 20th week of gestation the ratio of AF prolactin: serum prolactin ranges from 22:1 to 227:1 (Friesen et al. 1972). As pregnancy advances the AF prolactin levels fall but always remain higher than the maternal serum prolactin values (Friesen et al. 1972; Tyson et al. 1972).
It was possible that human prolactin might well occur in AF in a form which was immunoreactive (and so detectable by radioimmunoassay) but which was biologically inactive. Therefore the lactogenic activity of human AF has been investigated
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SUMMARY
Immunoreactive rat prolactin was detected in rat milk. Increasing volumes of milk decreased the percentage of 131I-labelled rat prolactin bound to antiserum in a manner parallel to the decreases produced by increasing log doses of standard hormone and blood serum. Rats suckling litters of 4, 8 or 12 pups were milked at various stages of lactation and prolactin concentrations (ng/ml) in milk varied significantly both with stage of lactation and with litter size. Mean prolactin levels were maximal on day 4 to day 15 and they decreased sharply near the end of lactation. At every stage of lactation litter size tended to influence prolactin concentrations with larger litters always being associated with more prolactin per millilitre of milk. Intraperitoneal injection of 1 mg bovine prolactin into lactating rats promptly caused the appearance of high levels of this foreign hormone in rat milk without significantly affecting the concentration of the native hormone.
