α-Melanotropin-like substances in the pituitary and plasma of Xenopus laevis in relation to colour change responses

Wilson, John F.; Morgan, Merrill A.

doi:10.1016/0016-6480(79)90204-1

Cited by 42 publications

(15 citation statements)

References 39 publications

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“…Despite the established role of melanocortins, mainly a-melanocortin (a-MSH), as the physiological regulator of integumental pigmentation in many vertebrate species, including fish, amphibians, reptiles and mammals, their significance for human pigmentation remained elusive until the1990s [35,37,97]. In poikilotherms, such as amphibians and reptiles, melanocortins stimulate rapid color change within minutes, allowing for camouflage in order to blend with the environment and evade predators, and to adjust body temperature in accordance with the climate [82,103,104,127]. The controversy about the role of melanocortins in human pigmentation stemmed from the assumption that melanocortins are endocrine factors that are secreted by the intermediate lobe of the pituitary gland, which is vestigial in humans.…”

Section: Introductionmentioning

confidence: 99%

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention

Abdel‐Malek

Swope

Starner

et al. 2014

Archives of Biochemistry and Biophysics

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Section: Introductionmentioning

confidence: 99%

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention

Abdel‐Malek

Swope

Starner

et al. 2014

Archives of Biochemistry and Biophysics

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“…This peptide stimulates the dispersion of melanin pigment granules in dermal melanophores, giving the animal a black appearance. In animals on a white background, the release of ␣-MSH is inhibited, and consequently, the pigment granules in the melanophore cell are aggregated around its nucleus, and the animal takes on a pale appearance (8,9). On a black background, the melanotrope cell diameter is about twice as large as on a white background (10), and the production of POMC and the secretion of its end product, ␣-MSH, are strongly enhanced (11).…”

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confidence: 97%

Pituitary Adenylate Cyclase-Activating Polypeptide Regulates Brain-Derived Neurotrophic Factor Exon IV Expression through the VPAC1 Receptor in the Amphibian Melanotrope Cell

2008

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In mammals, pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors PAC1-R, VPAC1-R, and VPAC2-R play a role in various physiological processes, including proopiomelanocortin (POMC) and brain-derived neurotrophic factor (BDNF) gene expression. We have previously found that PACAP stimulates POMC gene expression, POMC biosynthesis, and alpha-MSH secretion in the melanotrope cell of the amphibian Xenopus laevis. This cell hormonally controls the process of skin color adaptation to background illumination. Here, we have tested the hypothesis that PACAP is involved in the regulation of Xenopus melanotrope cell activity during background adaptation and that part of this regulation is through the control of the expression of autocrine acting BDNF. Using quantitative RT-PCR, we have identified the Xenopus PACAP receptor, VPAC1-R, and show that this receptor in the melanotrope cell is under strong control of the background light condition, whereas expression of PAC1-R was absent from these cells. Moreover, we reveal by quantitative immunocytochemistry that the neural pituitary lobe of white-background adapted frogs possesses a much higher PACAP content than the neural lobe of black-background adapted frogs, providing evidence that PACAP produced in the hypothalamic magnocellular nucleus plays an important role in regulating the activity of Xenopus melanotrope cells during background adaptation. Finally, an in vitro study demonstrates that PACAP stimulates the expression of BDNF transcript IV.

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“…Pigmentation has long been recognized for playing a role in camouflage and sun protection, but the extent of a-MSH involvement in regulation of basal skin tone is not yet firmly established. It is well known that injection of ca-MSH into a variety of animals including humans causes an increase in skin tone beyond basal levels (1,2), and there is evidence in some species that plasma a-MSH may correlate with changes in background and animal color (12)(13)(14), but these do not provide conclusive information with regard to the extent of MSH involvement in the setting or maintenance of basal tone. Support for the possible involvement of a-MSH in basal skin tone comes primarily from experiments in which removal of the pituitary gland induces pallor in fish, amphibians, and lower mammals (15)(16)(17)(18) and from anecdotal clinical reports, given without explanation or speculation, that humans become abnormally pale following the loss of pituitary function due to disease or following hypothesectomy for treatment of metastatic breast cancer (19 (11) by using fluorenylmethoxycarbonyl (Fmoc) chemistry on 4-methylbenzhydrylamine (MBHA)-linked polystyrene resin in combination with a standard simultaneous multiple peptide synthesis protocol (21,22).…”

mentioning

confidence: 99%

Combinatorial diffusion assay used to identify topically active melanocyte-stimulating hormone receptor antagonists.

Quillan

Jayawickreme

Lerner

1995

Proc. Natl. Acad. Sci. U.S.A.

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a-Melanocyte-stimulating hormone (av-MSH) is implicated in pigmentation, central nervous system and immune system functions, growth, mitogenisis, and melanoma. Evaluation of these roles has been hindered by the lack of a-MSH antagonists. A combinatorial chemistry-based diffusion assay is used to find random tripeptides that antagonize normal frog and human melanoma MSH receptors and to identify pharmacological groups responsible for receptor interaction. The a-MSH antagonist D-Trp-Arg-Leu-NH2 is used to demonstrate directly the contribution of MSH to normal skin tone in frogs following injection or topical application.a-Melanocyte-stimulating hormone (a-MSH) is potentially involved in numerous important physiological and pathological processes ranging from pigmentation to melanoma (1-9). These roles have not been closely examined, in part at least because of a lack of MSH receptor antagonists. Preliminary reports of compounds that inhibit a-MSH-induced darkening in Rana pipiens skin assays have been made (10), but it is unclear how receptor specific these compounds are or if they are effective in blocking responses to MSH in other species or in vivo. One method typically used to identify antagonists to peptide receptors has been to manipulate the size and sequence of the native peptide hormone. Another method has relied on random screening of thousands of compounds. In this report we describe the use of a combinatorial diffusion assay, an assay that separates molecules in time and space (11), to randomly search for tripeptide and tripeptide-like molecules that antagonize the ca-MSH receptor. The small and uncomplicated structure of these peptide antagonists provides useful structural information for determining receptor interactions.Pigmentary phenomena serve as an example of the many areas of study that stand to benefit from the development of specific MSH receptor antagonists. Pigmentation has long been recognized for playing a role in camouflage and sun protection, but the extent of a-MSH involvement in regulation of basal skin tone is not yet firmly established. It is well known that injection of ca-MSH into a variety of animals including humans causes an increase in skin tone beyond basal levels (1, 2), and there is evidence in some species that plasma a-MSH may correlate with changes in background and animal color (12-14), but these do not provide conclusive information with regard to the extent of MSH involvement in the setting or maintenance of basal tone. Support for the possible involvement of a-MSH in basal skin tone comes primarily from experiments in which removal of the pituitary gland induces pallor in fish, amphibians, and lower mammals (15-18) and from anecdotal clinical reports, given without explanation or speculation, that humans become abnormally pale following the loss of pituitary function due to disease or following hypothesectomy for treatment of metastatic breast cancer (19). However, the complex and far-reaching physiological interactions of the pituitary obscure demonstration...

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α-Melanotropin-like substances in the pituitary and plasma of Xenopus laevis in relation to colour change responses

Cited by 42 publications

References 39 publications

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention

Pituitary Adenylate Cyclase-Activating Polypeptide Regulates Brain-Derived Neurotrophic Factor Exon IV Expression through the VPAC1 Receptor in the Amphibian Melanotrope Cell

Combinatorial diffusion assay used to identify topically active melanocyte-stimulating hormone receptor antagonists.

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