How the tan is made
The tan MT-II produces is not a stain or a dye.
From receptor to pigment: how MT-II darkens skin
The tan MT-II produces is not a stain or a dye. It is the end of a real biological cascade: MT-II switches on MC1R, a messenger surge activates a master pigment gene, and that gene ramps up the enzymes that build melanin inside skin cells.
This unit follows that chain link by link, explains the crucial difference between protective and damaging melanin, and confronts the most dangerous myth around MT-II: that a chemical tan protects you from the sun.
Key terms
The melanin cascade
MC1R on a melanocyte sits at the top of a defined relay that ends in pigment. The relay below is the one described for the natural hormone alpha-MSH, and MT-II is a redesigned copy of that hormone core, so this is the route it is understood to take. Be clear about the limit: no study has measured a messenger, a gene or an enzyme after an MT-II dose. This is the best-characterised biology in the course and it is still borrowed from the natural ligand.
Follow the logic and the tan demystifies itself. The receptor surge does not "make pigment" directly; it flips a master gene (MITF), which switches on the enzyme genes, and tyrosinase then builds melanin from a common amino acid. The pigment is handed from melanocytes to surrounding keratinocytes inside melanosomes, carried along the melanocyte dendrites, where it shows up as darkening over days rather than minutes.
AdvancedWhy the tan appears gradually and outlasts the dose
Because the effect runs through gene transcription and enzyme synthesis, it cannot be instant. New enzyme has to be made, melanin has to accumulate, and pigment has to transfer to keratinocytes. That is why visible tanning took about five doses over two weeks in the original trial, and why colour outlasts dosing: the pilot measured increased pigmentation by reflectance and by eye one week after dosing ended. How much longer than that it lasts was not measured in anyone.