Hormone mélanotrope

See also: MSH

The hormone mélanotrope , or mélanotropine or mélanocortine (name more used) or MSH (for melanocyte stimulating hormone ), is a hormone secreted by the cells mélanotropes of the Hypophyse (former lobe) and the mélanocytes. It is the product of maturation of a pro-hormone, POMC, by specific enzymes called Pro-hormone convertase S.

There exist three types of MSH, the α-MSH and the γ-MSH (resulting from the maturation of the hormone corticotropin or ACTH) and the β-MSH (resulting from the maturation of the Lipotropine β-LPH).

In the cells mélanotropes of the pituitary gland one finds the α-MSH and β-MSH, whereas in the Mélanocyte S is maturée α-MSH only.

Structure

  • α-MSH: Ac-Ser-Tyr-Ser-Put-Lime-His-Phe-Arg-Trp-Gly-Lily-Pro-valley-NH2

  • β-MSH (human): Go-Lime-Lily-Lily-Asp-Lime-Gly-Pro-Tyr-Arg-Put-Lime-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-lily-Asp
  • β-MSH (porcine): Asp-Lime-Gly-Pro-Tyr-Lily-Put-Lime-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-lily-Asp
  • γ-MSH:
Tyr-Valley-puts-Gly-His-Phe-Arg-Trp-Asp-Arg-Phe-Gly

Effects

The MSH acts on the Mélanocyte S of the skin by causing the secretion of Mélanine in answer to rays UVA mainly.

Regulation

Mode of action

The effects of the MSH pass by its fixing on a membrane Récepteur specific called MCR (for melanocortin receptor ) expressed normally by the Mélanocytes of the skin. The fixing of the MSH to its receiver involves a way of intracellular indication implying the Calcium like Second messenger.

Physiopathology

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