The physicochemical properties of the melanophore-concentrating hormone (MCH) of teleost pituitaries were studied. It was found to be a heat-stable trypsin- sensitive peptide of about 1 700 daltons which was similar in charge, size and hydrophobicity to MSH. Partial purification by cation-exchange, gel-filtration and HPLC showed that it was not identical with any of the melanocyte-stimulating hormones (MSH's) of teleost pituitary, but the possibility that these peptides are structurally related could not be excluded. Both hypothalamic and pituitary forms of MCH were distinguished from the known neurohypophysial hormones by their size and their insensitivity to reduction with thiol-reagents. Complete purification of MSH's showed that these were present in greater amounts than was MCH in the pituitary. The implications of this are discussed recommending the hypothalamus rather than the pituitary for the purification of MCH. Since melanophore-concentrating activity could be masked in crude hypothalamic extracts, MCH may have a wider phylogeny than has been previously appreciated.
|Date of Award