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Department of Physiology, Queen's University, Kingston, Ontario, Canada K7L 3N6
(Received 20 May 1974)
It is well established that gonadal steroid hormones stimulate prolactin secretion and increase the level of prolactin in the blood (Meites, Lu, Wuttke, Welsch, Nagasawa & Quadri, 1972). Many studies of the factors affecting the level of prolactin in the blood have been performed with anaesthetized rats (Chen & Meites, 1970; Wuttke & Meites, 1970; Kalra, Fawcett, Krulich & McCann, 1973). However, since it is now reasonably well established that anaesthetic agents can change levels of prolactin in the circulation (Wakabayashi, Arimura & Schally, 1971; Ajika, Kalra, Fawcett, Krulich & McCann, 1972; Terkel, Blake & Sawyer, 1972), we decided to re-examine the effect of gonadal steroids upon plasma levels of prolactin in the unanaesthetized rat. Animals were castrated and prolactin levels were determined at three intervals with and without the administration of testosterone.
Young male rats
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The pituitary gland of the male adult rodent contains as much prolactin as that of immature females (Jones, Fisher, Lewis & VanderLaan, 1965), but the significance of its occurrence in the male is not clear. The effect of prolactin on male fertility was therefore studied in genetically dwarf mice (dwarf = dw and Ames dwarf = df).
The adenohypophysis of dwarf mice produces little or no prolactin, even when removed from hypothalamic inhibition (Bartke, 1965b). Female dwarf mice are sterile but can reproduce normally when prolactin is provided (Bartke, 1965a, 1966). In a non-inbred stock of df dwarfs, grafting normal mouse pituitary into the renal capsule increased the proportion of fertile dwarf males. This indicates a role of prolactin in male fertility. However, pituitary grafts, in addition to secreting prolactin, have pronounced growth hormone (GH) and some thyroid-stimulating hormone (TSH) activity (Hertz, 1959) and it is known that both GH
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SUMMARY
Prolactin—thyroid interaction was analysed in the second metamorphosis of Diemictylus viridescens. Intraperitoneal injections of either 3 μg thyroxine (T4) or 0·2 mg propylthiouracil (PTU) on alternate days failed to induce second metamorphosis in the red eft (land stage); 0·1 mg PTU inhibited prolactin-induced second metamorphosis. The effect of prolactin was facilitated by 0·1 μg T4. However, 0·5 μg T4 inhibited water-drive behaviour after initial stimulation of integumentary changes and water-drive. Larger doses of T4 (1–3 μg) proved fatal to the efts when given together with 0·5–40 μg prolactin.
The results indicate that a certain optimal level of thyroid hormone is needed for the initiation of second metamorphosis. Nevertheless, prolactin—thyroid antagonism, previously reported in tadpoles, also occurs in the newt. Second metamorphosis appears to be brought about by a reversal of the low prolactin—high thyroid level of the eft phase to a high prolactin—low thyroid level.
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SUMMARY
The influence of prolactin on the assay of human menopausal gonadotrophin (HMG) and human chorionic gonadotrophin (HCG) has been studied. Various bioassay methods were used and the experiments were conducted in two independent laboratories.
In hypophysectomized immature male rats the response of the ventral lobe of the prostate to HMG was not affected by simultaneous administration of prolactin. It was concluded that, in the case of urinary extracts, prolactin did not interfere with the specificity of this test for interstitial cell stimulating hormone activity.
Valid assays of HMG by the rat uterus and mouse uterus tests could be obtained in the presence of relatively large quantities of prolactin.
When HCG was assayed by the rat uterus test and by tests depending on the enlargement of the accessory reproductive organs in male rats, simultaneous administration of prolactin did not affect the results obtained.
In immature male rats prolactin did not prevent the regression of the accessory organs which occurs after castration.
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Introduction Prolactin-releasing peptide (PrRP) is a novel hypothalamic hormone, initially identified by Hinuma et al. (1998) by the method of ‘reverse’ pharmacology. A 31-amino-acid peptide (PrRP31), with no significant homology
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ABSTRACT
Immunoreactive tissue kallikrein was co-localized with prolactin in all the eleven prolactin-secreting adenomas of the human anterior pituitary gland examined in this study. The intracellular distribution of immunoreactivity in the prolactin-secreting cells suggests that tissue kallikrein is located within the Golgi complex of these cells. Both the intracellular hormone-processing action and the kininogenase activity of tissue kallikrein may be of functional importance in human prolactinomas.
Journal of Endocrinology (1990) 124, 327–331
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SUMMARY
The pattern of prolactin secretion was determined throughout the development of the male mouse. Levels of prolactin were at their lowest from birth to 20 days of age. A dramatic increase in serum prolactin occurred during pubertal maturation coincident with rapid growth of the accessory organ system. These events preceded the pubertal rise in the level of serum testosterone that is characteristic of this species.
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ABSTRACT
Long-term ovariectomized rabbits were given injections of progesterone and prolactin in an alternating sequence (progesterone for 5 days, prolactin for 4 days and progesterone for 5 days) to test the hypothesis that each of these hormones acts to increase the other's receptor, resulting in a positive feedback process whereby prolactin augments the progesterone-dependent increase in the mRNA for the uterine protein, uteroglobin. The results of this study support the hypothesis, in that the experimental rabbits produced exceptionally large concentrations of uteroglobin.
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Department of Animal Biology and Mari Lowe Center for Comparative Oncology Research, Cell and Molecular Biology Program, Department of Pathology, Inserm, Department of Cell Biology, Biomedical Graduate School, University of Pennsylvania, 380 S University Avenue, Philadelphia, Pennsylvania 19104, USA
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Introduction The prolactin receptor (PRLr) is a member of the cytokine receptor superfamily that transduces the signals of the pituitary hormone PRL, which is implicated in numerous biological functions (including mammary gland development
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SUMMARY
The response of rabbit mammary glands to intraductally-injected prolactin preparations has been investigated with a view to developing an assay procedure for prolactin, based on milk formation in mammals. Milk was clearly detectable in the glands by the 3rd day after injection of prolactin, and there was evidence of an increase in response with increased dose, but the variability so far encountered has been high. Intraductal injection of pituitary extracts rich in activities other than that of prolactin did not lead to milk formation.
