AspThrMetArgCysMetValGlyArgValTyrArgProCysTrpGluVal (melanin concentrating hormone, MCH) and several fragment analogs (MCH1-14, MCH5-17, MCH5-14) were synthesized and their biological activities determined in a very sensitive fish skin bioassay. The potency ranking and minimum effective doses of the peptides were determined to be: MCH1-17 (10-12M) >< MCH5-17 (10-12M) > MCH1-14 (10-11M) > MCH5-14 (2 × 10-10M). The melanosome aggregating activity of MCH could be completely reversed by a 100-fold higher concentration of ≺-MSH. MCH was self-antagonized in a dose-related manner by higher concentrations of the peptide as was the activity of the MCH1-14 fragment analog. The MCH activities of the MCH5-17 and MCH5-14 analogs were not compromised by even the highest concentrations of the peptides employed. The MSH-like activity of MCH appears to relate to the N-terminus of the peptide whereas MCH activity is more a function of the C-terminus of the hormone. Self- antagonism of MCH at high concentrations appears to relate to the N-terminal tetrapeptide, which is responsible for the intrinsic MSH-like activity of the hormone.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)