Source comparison
Melanocortin Receptor Selectivity: MT-I vs MT-II
Melanotan-1 and melanotan-II are both synthetic analogs of α-melanocyte-stimulating hormone (α-MSH), but their pharmacological profiles diverge at the receptor level. MT-I binds selectively to MC1R (the primary melanogenesis receptor in melanocytes) and MC5R (
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- Melanotan-1 and melanotan-II are both synthetic analogs of α-melanocyte-stimulating hormone (α-MSH), but their pharmacological profiles diverge at the receptor level. MT-I binds selectively to MC1R (the primary melanogenesis receptor in melanocytes) and MC5R (involved in sebaceous gland function) with EC50 values in the low nanomolar range. Approximately 0.2–0.5 nM for MC1R. MT-II, by contrast, activates all four melanocortin receptor subtypes involved in mammalian physiology: MC1R, MC3R (energy homeostasis), MC4R (appetite regulation and cardiovascular tone), and MC5R.
- That four-receptor activation pattern means MT-II produces melanogenesis alongside appetite suppression, increased energy expenditure, and transient blood pressure elevation. Effects mediated primarily through MC4R signaling in the hypothalamus. For pigmentation-focused studies, those are confounding variables. MT-I eliminates them. A 2006 study published in Peptides demonstrated that MT-I produced equivalent melanogenesis to MT-II at comparable doses but with no detectable MC4R-mediated effects in rodent models. A finding consistently replicated across multiple species.
- The structural difference is subtle but pharmacologically decisive: MT-I retains the core α-MSH sequence responsible for MC1R binding but lacks the conformational flexibility that allows MT-II to fit into MC3R and MC4R receptor sites. That rigidity is intentional. It's what produces the selective binding profile researchers rely on when isolating melanogenesis as the dependent variable.