title: Immunological evidence for multiple forms of alpha-melanotropin (alpha-MSH) in the pars intermedia of the Australian lungfish, Neoceratodus forsteri.
abstract: Acid extracts of individual pars intermedia from the Australian lungfish, Neoceratodus forsteri, were fractionated by gel filtration chromatography and analyzed for alpha-melanotropin (alpha-MSH) immunoreactivity. In these studies a C-terminal-specific alpha-MSH radioimmunoassay (RIA) was used. Following gel filtration chromatography on a Sephadex G-75 column, a major peak of immunoreactive alpha-MSH-sized material was detected. On the average there was 338 +/- 72 pmol (SD) of immunoreactive alpha-MSH per lungfish pars intermedia (n = 3). Following gel filtration the immunoreactive alpha-MSH was further analyzed by reverse-phase high-performance liquid chromatography (HPLC). Three peaks of immunoreactivity were detected. These peaks were designated Peaks 1, 2, and 3. The retention times of these peaks corresponded to, respectively, mammalian ACTH(1-13)amide, N-acetyl-ACTH(1-13)-amide, and N,O-diacetyl-ACTH(1-13)amide. Peaks 2 and 3 represented approximately 95% of the immunoreactive alpha-MSH recovered. Analysis of immunoreactive Peaks 2 and 3 by cation-ion-exchange indicated that both peaks had a net charge of +3 at pH 2.5. Since O-acetyl groups are sensitive to high pH, Peak 3 was incubated for 1 hr at 37 degrees in 0.01 N NaOH, pH 12. Under these conditions, Peak 3 eluted with the same retention time as untreated Peak 2. Collectively, these results indicate that Peaks 2 and 3 correspond to mono- and diacetylated lungfish alpha-MSH, respectively.
authors.affiliation: University of Denver, Department of Biological Sciences, Colorado 80208.
authors.forename: R M
authors.initials: RM
authors.lastname: Dores
authors.forename: J M
authors.initials: JM
authors.lastname: Joss
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002852:Chromatography, Ion Exchange; D005399:Fishes / Q000378:metabolism*; D010902:Pituitary Gland / Q000032:analysis*; D011863:Radioimmunoassay; D000521:alpha-MSH / Q000032:analysis*
chemical_list: D000521:alpha-MSH