Intracellular acetylation of desacetyl αMSH in the xenopus laevis neurointermediate lobe

Me, Goldman; Yp, Loh

doi:10.1016/0196-9781(84)90178-5

Cited by 12 publications

(3 citation statements)

References 15 publications

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“…We find no difference in the acetylation status when newly synthesized peptides are compared to immunoreactive peptides, and therefore see no reason to place these peptides in 'independent' pools. The results of Goldman and Loh [10] indicate that in vitro inhibition of secretion with dopamine leads to an accumu lation of acetylated peptide in the tissue. While a rapid ac cumulation of acetylated peptide in release-inhibited lobes would certainly argue for a major role for intracellular ace tylation, we show that in fully white-background-adapted Xenopus (where secretion is under tonic inhibition for 3 weeks) the major form of immunoreactive MSH in the in termediate lobe is still des-acetyl-a-MSH.…”

Section: Discussionmentioning

confidence: 97%

“…Goldman and Loh [10], in an in vitro study with neurointermediate lobes of black-background-adapted animals, conclude that the major route of acetylation of MSH in Xenopus is an intracellular route analogous to that reported for mammals. They, too, find that des-acetyl-a-MSH is the major immunoreactive form of MSH in the tissue and, to account for the enhanced level of a-MSH in the medium, they evoke the concept of inde pendent 'pools' of secretory peptides.…”

Section: Discussionmentioning

confidence: 99%

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N-Terminal Acetylation of Melanophore-Stimulating Hormone in the Pars intermedia of <i>Xenopus laevis </i>Is a Physiologically Regulated Process

Kemenade¹,

Jenks²,

Smits³

1987

Neuroendocrinology

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The N-terminal acetylation of melanophore-stimulating hormone (MSH) increases the melanotropic potency of the peptide. This modification may be important in amphibians, where MSH causes skin darkening during adaptation to black background. This study examines the acetylation status of the peptide in the toad Xenopus laevis under different conditions of background adaptation. Acetylated and nonacetylated α-MSH were analyzed by high-performance liquid chromatography and quantified by radioimmunoassay. The acetylation status of α-MSH was analyzed in tissue, in plasma and in media obtained from in vitro incubation of neurointermediate lobe tissue. Nonacetylated MSH is the major form of α-MSH in tissue from both black- and white-background-adapted animals. In plasma of black-adapted animals only acetylated α-MSH could be detected. Plasma MSH levels of white-adapted animals were barely detectable. Analysis of peptides secreted during in vitro incubations of neurointermediate lobe tissue from black-adapted animals showed that the relative contribution of α-MSH to the immunoreactive profile was considerably enhanced, which supports the concept that acetylation of MSH in Xenopus is associated with the secretory process. Acetylation capacity of tissue from white-adapted animals was much lower and only after several days on black background was full capacity acquired. It is suggested that de novo biosynthesis of acetylation enzymes may be necessary for the acquisition of the acetylation capacity. Transfer of black animals to white background caused a rapid decrease in acetylation capacity, which suggests that factors involved in the rapid inhibition of secretion might also regulate acetylation. This finds support in the observation that dopamine was effective in partially inhibiting the acetylation capacity of this tissue. It is concluded that the acetylation of MSH in the pars intermedia of X. laevis is a regulated process related to physiological parameters concerning background color.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

N-Terminal Acetylation of Melanophore-Stimulating Hormone in the Pars intermedia of <i>Xenopus laevis </i>Is a Physiologically Regulated Process

Kemenade¹,

Jenks²,

Smits³

1987

Neuroendocrinology

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“…Even so, the production of acetylated forms of -MSH by human pituitary cells cannot be discounted from these studies, if the acetylation step occurs predominantly during peptide release (Martens, Jenks & van Overbeeke, 1981). However, this process appears to be the exception rather than the rule, since acetylation occurs intracellularly in the rodent and frog pars intermedia (Glembotski, 1982;Jenks, van Daal, Scharenberg et al 1983;Goldman & Loh, 1984).…”

Section: Discussionmentioning

confidence: 89%

Demonstration of desacetyl α-melanocyte-stimulating hormone in fetal and adult human anterior pituitary corticotrophs

Coates

Doniach²,

Holly³

et al. 1989

Journal of Endocrinology

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Immunocytochemistry, radioimmunoassay and high-performance liquid chromatography (HPLC) techniques have been used in combination to investigate the presence of immunoreactive (ir)-alpha-MSH in the normal human pituitary gland, and to investigate the possible origin of these cells from the fetal pars intermedia. Two separate antisera to alpha-MSH were employed in immunocytochemistry to distinguish between authentic alpha-MSH and the desacetyl form. Only desacetyl alpha-MSH was detected in the pituitary gland of fetal and adult man, in both the pars (zona) intermedia and the pars anterior. In the fetus, a large proportion of the ACTH-containing cells of the anterior lobe also contained ir-alpha-MSH, while ir-alpha-MSH containing cells were more sparse in adults. Radioimmunoassay of acid extracts of adult pituitary tissue showed alpha-MSH levels representing less than 0.05% of the ACTH content of the gland. HPLC analysis of these extracts confirmed that only the desacetyl form was present. These results suggest that alpha-MSH peptides are synthesized by anterior lobe cells of the human pituitary gland, which are not derived from the fetal pars intermedia. Possible regulatory mechanisms affecting cells which contain ir-alpha-MSH are discussed, and by comparison with the intermediate lobe of other species it is concluded that there is little evidence for a true intermediate lobe in the human pituitary gland.

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Isolation of α-melanotropin from the pars intermedia of the larval amphibian, Ambystoma tigrinum

Dores¹,

Schenk²,

Rothenberg³

1987

General and Comparative Endocrinology

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Intracellular acetylation of desacetyl αMSH in the xenopus laevis neurointermediate lobe

Cited by 12 publications

References 15 publications

N-Terminal Acetylation of Melanophore-Stimulating Hormone in the Pars intermedia of <i>Xenopus laevis </i>Is a Physiologically Regulated Process

N-Terminal Acetylation of Melanophore-Stimulating Hormone in the Pars intermedia of <i>Xenopus laevis </i>Is a Physiologically Regulated Process

Demonstration of desacetyl α-melanocyte-stimulating hormone in fetal and adult human anterior pituitary corticotrophs

Isolation of α-melanotropin from the pars intermedia of the larval amphibian, Ambystoma tigrinum

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