α-Melanotropin (α-MSH) retains less than 1% of its original activity after a 60 min incubation with 10% rat brain homogenate. [Nle4, D-Phe7]-α-MSH is nonbiodegradable in rat serum (240 min incubation) and still maintains 10% of its original activity in 10% rat brain homogenate (240 min incubation). The related fragment analogue, Ac-[Nle4, D-Phe7]-α-MSH4-10-NH2, retains 50% of its activity after a 240 min incubation in rat brain homogenate, whereas Ac-[Nle4, D-Phe7]-α-MSH4-11-NH2 is totally resistant to inactivation by rat brain homogenate. Both [Nle4, D-Phe7]-fragments are resistant to degradation by rat serum, but [Nle4]-α-MSH, Ac-[Nle4]-α-MSH4-10-NH2 and Ac-[Nle4]-α-MSH4-11-NH2 are rapidly inactivated under both conditions. The cyclic melanotropin, [Cys4,Cys10]-α-MSH, is inactivated in rat brain homogenate as is the shorter Ac-[Cys4,Cys10]-α-MSH4-10-NH2 analogue, but neither cyclic melanotropin is inactivated upon incubation in serum from rats. Ac-[Cys4,D-Phe7,Cys10]-α-MSH4-10-NH2 is resistant to inactivation by either rat serum or a brain homogenate. Some of these melanotropin analogues may provide useful probes for the localization and characterization of putative melanotropin receptors in both the central nervous system and peripheral tissues.
- Hormone stability
- Melanocyte stimulating hormone
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience