Pituitary Melanocyte-stimulating Hormone Research Articles

Cloning and sequence analysis of a hypothalamic cDNA encoding a D 1c dopamine receptor in tilapia

Physiological and pharmacological studies have indicated that during acid stress a D 1-like dopamine receptor becomes functional on intermediate pituitary melanocyte-stimulating hormone cells of tilapia ( Oreochromis mossambicus). As a first step towards physiological expression studies we isolated a D 1-like dopamine receptor from a tilapia hypothalamus cDNA library. Construction of a phylogenetic tree of most of the D 1-like receptors known in human, rat, Xenopus, goldfish and Drosophila revealed that the here presented clone is most likely the tilapia equivalent of the Xenopus D 1c dopamine receptor.

Melanocyte-Stimulating Hormone and Persistent Tardive Dyskinesia: A Hypothesis

An increased incidence of abnormal perioral movements has recently been reported in drug-naive pinealectomized rats with further accentuation of these movements following administration of haloperidol. Analysis of the temporal course of the development of the perioral dyskinetic movements revealed that the onset of these movements occurred within 4 days postoperatively and peaked at 3 weeks to plateau over the following 4-6 weeks. Increased pituitary Melanocyte-stimulating hormone (MSH) content has been reported in pinealectomized rats. Elevation of MSH content in the pinealectomized rats occurred within 3 days of surgery and was followed by normalization within 4 weeks. These findings suggest that compensatory mechanisms involving hypothalamic-pituitary MSH release must have been activated to induce normalization of pituitary MSH levels. Moreover, reduction of pituitary MSH levels may have coincided with attenuation in the severity of the perioral dyskinetic movements. It is possible that the development of tardive dyskinesia (TD) may in part be associated with increased brain and plasma MSH levels and that impaired hypothalamic-pituitary regulatory mechanisms of MSH release may be associated with persistent TD. The pineal gland may be implicated in this process as diminished melatonin secretion may be associated with disinhibition of MSH release. Thus, the above hypothesis complements and extends the recently presented "melatonin hypothesis" and suggests that research of pineal-hypothalamic interactions may be crucial to the further understanding of TD.

Seborrhea and Persistent Tardive Dyskinesia

The following communication concerns two schizophrenic patients with Tardive dyskinesia (TD) in whom fluctuations in the severity of the dyskinesias were accompanied by changes in the severity of the seborrheic skin lesions. Since seborrheic dermatitis may be associated with increased plasma melanocyte-stimulating hormone (MSH) level, these observations suggest an association between the severity of TD and increased pituitary MSH release. In addition, TD may be associated with hypothalamic-pituitary dysfunction of MSH autoregulation.

Increase in pituitary melanocyte-stimulating hormone activity of genetically obese (ob/ob) mice.

Melanocyte-stimulating hormone (MSH) activity was measured in the pituitaries of genetically obese and lean control mice using the frog skin bioassay. Obese mice pituitaries demonstrated very significantly elevated levels of biologically active MSH when compared to their lean littermates. These results support the hypothesis that the elevated levels of pituitary hormones found in obese mice possesses true biological activity.

Serum Melanocyte-Stimulating Hormone Levels and Pituitary Melanocyte-Stimulating Hormone Content during Pseudopregnancy in the Rat*

Pseudopregnancy (PSP) was induced in rats by vaginal stimulation and the levels of MSH in serum and pituitary were examined. One hour after vaginal stimulation, the serum MSH level was increased, and a cyclical variation was observed by the second day of PSP. There were two surges of about 50 pg/ml, one in the morning and the other at night. On the sixth day of PSP, the pattern of serum levels still showed two peaks, but while the nocturnal peak remained at 50 pg/ml, the diurnal value was halved. The pituitary MSH content also underwent cyclical variations; the lowest levels coincided with the peak levels in serum. These observations raise the possibility that MSH is involved in PSP.

Tannic acid-induced dissociation of pituitary melanocyte-stimulating hormone and adrenocorticotropic hormone levels

1. Tannic acid was fed to young male and female laboratory mice at an 8% concentration (wt/wt) in ground food for 5 or 10 weeks duration. 2. Bioassays of pituitary melanocyte-stimulating hormones (MSH) and adrenocorticotropic hormone (ACTH) levels at autopsy revealed significantly elevated levels of pituitary MSH accompanied by significantly reduced levels of pituitary ACTH. 3. The results confirm a suspected dissociation of pituitary secretion of MSH and ACTH.

Reversal by Vasotocin of Pinealectomy and Constant Light Effects on the Pituitary Melanocyte-Stimulating Hormone (MSH) Content in the Mouse

A single injection of 1 pg synthetic arginine vasotocin (AVT) into the third ventricle of the mouse completely prevented the pituitary MSH increase which occurs seven days after pinealectomy or 24 h after exposure to constant light. The same concentration of AVT injected into the third ventricle of normal mice markedly decreased the pituitary MSH content at 20 min following the injection. The present results suggest that AVT injected into the third ventricle of the mouse inhibits synthesis and/or release of MSH-release inhibiting factor (MIF).

RE-INTRODUCTION AND EVALUATION OF AN ACCURATE, HIGH CAPACITY BIOASSAY FOR MELANOCYTE-STIMULATING HORMONE USING THE SKIN OF ANOLIS CAROLINENSIS IN VITRO

A simple and rapid assay for the quantitative determination of melanocyte-stimulating hormone (MSH) activity, using skin fragments of the lizard Anolis carolinensis in vitro, is described in detail. This assay, in which a quantal response (e.g. induction of a brownish-green colour) can be detected by visual observation, allows determination of MSH activity in up to 50 samples/day by one person, using the skin of one lizard. The mean dose found to induce this colour change was 0-15 ng synthetic alpha-MSH/ml (range 0-02-0-5 ng/ml). The assays shows high accuracy, reproducibility and specificity. Anterior and posterior lobe hormones as well as pituitary catecholamines do not interfere with the determination of pituitary MSH activitymthe method is compared with the assay using hypophysectomized frogs (Rana pipiens) in vivo. Determinations of MSH in pituitary extracts by both methods gave quantitatively similar results when determined with alpha-MSH as the reference substance. However, when beta-seryl MSH was used as a reference, the two assays gave different results for the MSH activity of the pituitary extractsmthis indicates that MSH from the rat pituitary gland has a biological activity similar to that of alpha-MSH rather than to that of beta-seryl MSH.

A diurnal rhythm in melanocyte-stimulating hormone content of the rat pituitary gland and its independence from the pineal gland.

Resting pituitary melanocyte-stimulating hormone (MSH) content was studied in adult rats kept under a controlled 14 h light-10 h dark regimen. A diurnal rhythm was found in pituitary MSH levels, showing peak values at 4.00-6.00 p.m., and low values during darkness and the beginning of the light period. The normally occurring fall in pituitary MSH content between 6.00 p.m. and midnight was also found in rats exposed to a prolonged photoperiod. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy, as well as pinealectomy, did not block the rhythm in pituitary MSH, and had no effect on pituitary MSH content. In addition, melatonin administered i.v. did not affect pituitary MSH levels, either when MSH activity was tested on the Anolis skin in vitro, or when the in vivo assay with hypophysectomized frogs (Rana pipiens) was used. It was concluded that the diurnal rhythm in pituitary MSH content is not directly related to the light-dark cycle and is not controlled by pineal melatonin or any otherpineal factor.

Plasma and pituitary MSH levels in the rat after lesions of the hypothalamus.

The long-term effect of hypothalamic lesions onplasma and pituitary levels of melanocyte-stimulating hormone (MSH) was examined in male rats. Lesions of the paraventricular nuclei (PVN) produced a large increase in both plasma and pituitary MSH levels, whereas lesions of the supra-optic nuclei had little effect. These results support the idea that MSH secretion is under an inhibitory control by the hypothalamus and suggest that the PVN are involved. The PVN may be involved in the release or production of an MSH release inhibiting factor (MIF), although the present results do not exclude the possibility that the PVN control MSH secretion through a direct innervation of the pars intermedia.

Tannic acid-induced alterations in mouse growth and pituitary melanocyte-stimulating hormone activity

Male albino mice were fed a diet containing 5 or 8% ( w w ) tannic acid in ground laboratory chow. Initial weights of mice ranged from 7 to 18 g and the duration of feeding from 3 to 8 wk. Body weights were taken at weekly intervals for all animals. At autopsy weights were taken of the testes, adrenals and pituitary glands and the latter were reserved for subsequent frog skin bioassay of melanocyte-stimulating hormone (MSH). The two test groups with initial body weights of 17.5–18.3 g demonstrated depressed growth initially, but had reached the body weight of untreated mice at time of autopsy. These groups showed no meaningful difference in testes, adrenal or pituitary weights or in pituitary MSH activity. Animals with the lowest initial weights (7–11.3 g) had continued depressed growth until the time of autopsy and exhibited a significant increase in pituitary MSH activity. It appears that young mice may be more susceptible to the effects of feeding tannic acid. The increase in pituitary MSH activity may be considered as evidence of the toxic effect of prolonged feeding of tannic acid, possibly occurring at the level of the hypothalamus.

MSH Activity in Plasma and Pituitaries of Rats with Large Hypothalamic Lesions

The effect of medial basal hypothalamic lesions on plasma and pituitary melanocyte-stimulating hormone (MSH) was determined in albino rats. 32 days postoperatively, plasma levels of MSH were elevated

Behavioral Aspects of Melanocyte-Stimulating Hormone (MSH)

Publisher Summary This chapter explores the behavioral aspects of melanocyte-stimulating hormone (MSH). The pituitary hormone MSH is tested in several different behavioral systems. MSH is a hormone(s) whose presence has persisted in the pituitary gland of vertebrates from very low forms to man. The primary function of MSH in higher mammals no longer seems to be pigmentary, but this is not sufficient reason to assume that MSH has no role in mammals or that the effects of MSH can be ascribed to corticotrophin (ACTH). Although MSH is known to play a vital role in amphibians such as the frog, an important function for MSH in mammals such as the rat is not well recognized. The frog better adapts to the environment by changing the color of its skin, an effect mediated by MSH. Extra-pigmentary effects of MSH upon bodily processes other than the central nervous system (CNS) are described by several investigators, including ourselves. It is speculated that during the course of evolution, MSH has maintained its “adaptive” value for the organism, but that this may apply only to simple tasks. The conclusion is reached that in mammals MSH exhibits definite extra-pigmentary actions upon behavior.

Effects of acute and chronic administration of DDT upon pituitary melanocyte-stimulating hormone (MSH) activity

1. 1. Technical 2,2-bis ( p-chlorophenyl)-1,1,1-trichloroethane(DDT) was administered to rats either in corn oil as a single oral dose (100 mg. per kg.) or through chronic feeding (500 p.p.m. in ground food). 2. 2. Assay of pituitary melanocyte-stimulating hormone (MSH) 4, 12, 24, 72, and 96 hours after single-dose administration revealed a significant reduction in pituitary MSH activity at 4 hours followed by gradually increasing pituitary levels of this hormone until, after 72 and 96 hours, the hormone had increased significantly above the level of the control animals. 3. 3. Rats fed a diet containing DDT showed a significantly increased pituitary MSH activity after 1 month with no significant difference in this hormone after 2 months of administration. 4. 4. These effects are proposed to result from a DDT interference with the normal hypothalamic control of pituitary MSH secretion.

Quantification of ultrastructural changes in the 'melanocyte-stimulating hormone cell' of the pars intermedia of the pituitary of Xenopus laevis, produced by change of background colour.

SUMMARY The fact that the transfer of amphibians between black and white backgrounds causes the 'melanocyte-stimulating hormone (MSH) cells' of the pars intermedia of the pituitary to undergo considerable morphological change has been established for some time. The application of morphometric techniques to the 'MSH cells' of Xenopus has permitted the quantitative analysis of these changes at the ultrastructural level. Of the nine classes of organelle selected for analysis in these cells, three, namely nucleus, plasma membrane and dense bodies, showed no statistically significant changes. The remaining classes of organelle all showed significant changes in the percentage of the total cell volume that they occupied, although not all the organelles changed at the same rate. Transfer of animals from a white to a black background for up to 12 days was associated with increase in the percent volume of rough endoplasmic reticulum, Golgi membranes, Golgi granules and mitochondria and with a decrease in the percent volume of the fibrous granules. Return of animals to a white background after 6 days on a black background produced a reversal of the above changes with return to, or close to, white background (control) levels. This quantitative ultrastructural approach also highlights discrepancies in both the rate and magnitude of the changes in some of the organelles and related non-morphological parameters previously reported, e.g. the size of the rough endoplasmic reticulum and the rate of incorporation of labelled amino acid into protein; or the numbers of fibrous granules and the levels of detectable pituitary MSH. Some possible interpretations of these discrepancies are discussed.

Release of pituitary melanocyte-stimulating hormone by the oxytocin fragment, H-Cys-Tyr-Ile-Gln-Asn-OH

The effect of the pentapeptide H-Cys-Tyr-Ile-Gln-Asn-OH to act like melanocyte-stimulating hormone-releasing factor (MSH-RF) was studied. This peptide decreases at ng amounts the MSH content of the rat pituitary and increases plasma MSH concentration. This agent also stimulates the release of MSH in animals with eminence lesion, indicating a direct action of the pentapeptide on the gland.

Formation of A Melanocyte-Stimulating Hormone-Release Inhibiting Factor By Hypothalamic Extracts from Rats

Median eminence extracts from male rats induced a drop in pituitary melanocyte-stimulating hormone (MSH) when injected into recipient animals because they evoked the release of MSH. This effect was lost if the extracts were incubated for 2.5 h. Incubation was shown to produce a factor (IF) which inhibited the release of MSH. Two agents are responsible for this reaction, one which is thermolabile and non-diffusible and the other heat-stable and diffusible. The non-diffusible fraction is associated with microsomes. Both agents are present in hypothalamic extracts but not in cerebral cortex extracts. Oxytocin and lysine-vasopressin can act as the heat-stable agent and form IF when incubated with the non-diffusible fraction. This system has a pH optimum between 7 and 8 and the amount of IF formed increases both with time and with the amount of non-diffusible fraction. It is suggested that IF is formed by an enzyme present in hypothalamic neurosecretory neurones from a precursor molecule.

Influence of DDT upon pituitary melanocyte-stimulating hormone (MSH) activity in the anuran tadpole

Anuran tadpoles exposed to DDT at sublethal concentrations were found to have significantly increased pituitary melanocyte-stimulating hormone levels when compared with control animals. An effect of DDT upon the hypothalamus is postulated.

Measurement and electrophoretic study of melanocyte-stimulating hormone (MSH)-like substances in human pregnancy urine.

ABSTRACT A procedure for the determination of melanocyte-stimulating hormone (MSH)-like activity in human urine is reported. It consists of adsorption of the activity by Amberlite CG-50 cationic exchange resin at pH 3.5, elution of the adsorbed activity from the resin by IN ammonium hydroxide and the removal of an unidentified inhibitor by zone electrophoresis on Pevikon. The in vitro bioassay procedure using isolated Rana pipiens skin was used for the determination of the MSH-like activity. Minute quantities, 20–40 U, of MSH of human origin added to the urine specimen can be extracted with a recovery of 80%. The urine of normal men and nonpregnant women did not show any activity attributable to pituitary MSH. In the urine of normal pregnant women, 2 minor fractions resembling pituitary MSH's could be detected electrophoretically. The mean total value of these fractions from the urine specimens of 8 pregnant women was 13.3±4.3 MSH U/24 hr. The major portion of the MSH-like activity of pregnancy urine beha...

Post-natal development of rat pituitary melanocyte-stimulating hormone and the effect of light.

LIGHT influences the level of melanocyte-stimulating hormone (MSH) in the pituitary gland of rats1. The MSH content increases after a period of constant illumination and is lowered by a period of darkness. This response requires the presence of the pineal gland and may involve melatonin and the MSH-release inhibiting factor (MIF) of the hypothalamus. During a study of the relation of the pars intermedia of the pituitary to the production and release of MSH2,3, we followed the content of MSH in the neurointermediate lobe throughout the post-natal development of the rat, from 7 days to 6 months.