AN ANALYSIS OF THE PROOPIOMELANOCORTIN SYSTEMS IN THE PITUITARY OF THE SQUAMATE REPTILE LACERTA-GALLOTI

Acid extracts of the pars intermedia of the squamate reptile Lacerta g alloti were screened for immunoreactive forms of proopiomelanocortin ( POMC)-related end products following Sephadex G-50 column chromatograp hy. alpha-MSH-sized end products were detected with a Val-NH2, C-termi nal-specific RIA, and beta-endorphin-sized end products were detected with a separate C-terminal-directed RIA. Five peaks of alpha-MSH-relat ed immunoreactivity were isolated following fractionation by reversed- phase HPLC. Based on a comparison of the reversed-phase HPLC propertie s and the net positive charges (pH 2.75) of the Lacerta forms of alpha -MSH to those of the mammalian forms of alpha-MSH and Anolis carolinen sis ACTH(1-13)NH2, it appears that the N-acetylation of alpha-MSH is a major post-translational processing event in the pars intermedia of L . galloti. Although multiple forms of beta-endorphin were detected in the pars intermedia of L. galloti following cation-exchange chromatogr aphy, the low levels of N-acetylated beta-endorphin detected with an N -acetyl-specific beta-endorphin RIA indicate that the N-acetylation of beta-endorphin in this species is a minor post-translational processi ng event. This pattern of POMC processing in the pars intermedia of L. galloti is similar to the processing events observed for the turtle P seudemys scripta, but distinct from the processing events observed in the squamate reptile A. carolinensis. (C) 1994 Academic Press, Inc.