Apparent Co‐Sequestration of Immunoreactive Corticotropin, α‐Melanot opin, and γ‐Lipotropin in Hypothalamic Granules

A. Barnea, G. Cho, J. C. Porter

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Abstract: In the present study, the question of whether immunoreactive α‐melanotropin (α‐MSH1), corticotropin (ACTH1), and β‐melanotropin (β‐MSH1) are co‐sequestered in hypothalamic granules of adult male rats was addressed. When a 900 ×g supernatant fluid prepared from a hypothalamic homogenate was fractionated on continuous sucrose density gradients under non‐equilibrium Conditions, two populations of particles containing α‐MSH1, ACTH1, or β‐MSH1 Were observed. However, when fractionated under equilibrium conditions, the two populations of particles containing α‐MSH1 ACTH1, or β‐MSH1 were recovered as a single band. This sedimentation characteristic indicates that the particles containing a given peptide differ in size but are similar in density. In their sedimentation, the small particles containing α‐MSH1, ACTH1, and β‐MSH1 are indistinguishable from granules containing α‐MSH1, whereas the large particles containing α‐MSH1 (ACTH1, and β‐MSH1 are indistinguishable from synaptosomes containing α‐MSH1, β‐MSH1 had an apparent molecular weight (M.W.) of about 5,000, which is similar to that of γ‐lipotropin. ACTH1 was comprised of three species of molecules: big (M.W. ≥ 10,000), 5.7K (M.W. ≌ 5,700), and 4.5K (M.W. ≌ 4,500). Big ACTH was the predominant and 5.7K ACTH the minor component of ACTH1 present in granules as well as in synaptosomes. These results are suggestive that α‐MSH, ACTH and its precursors, and γ‐lipotropin are co‐sequestered in hypothalamic granules.

Original languageEnglish (US)
Pages (from-to)1083-1092
Number of pages10
JournalJournal of Neurochemistry
Volume36
Issue number3
DOIs
StatePublished - Mar 1981

Keywords

  • Corticotropin
  • Granules
  • Hypothalamus
  • Synaptosomes
  • α‐Melanotropin
  • γ‐Lipotropin

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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