Galanin and Galanin Extended at the N-Terminus with Seven and Nine Amino Acids Are Produced in and Secreted from the Porcine Adrenal Medulla in almost Equal Amounts*

Abstract

Galanin is present in high concentrations in porcine adrenals, but nothing is known about the processing and secretion of other products of the 123-amino acid precursor preprogalanin. Using, in combination, RIA against galanin, a variety of chromatographic procedures, mass spectrometry, and amino acid sequencing, we studied the processed and the secreted products of preprogalanin. From the tissue extracts we isolated in equimolar amounts and sequenced two major pools of galanin immunoreactive peptides: galanin and two N-terminally extended forms, preprogalanin-(24-61) and preprogalanin-(26-61). The same peptides were identified upon gel chromatography and analytical HPLC in effluents collected during electrical stimulation of the intact splanchnic nerve supply of an isolated perfused preparation of porcine adrenals. The processing of preprogalanin in porcine adrenals thus includes the formation and release of galanin, preprogalanin-(24-61), and preprogalanin-(26-61). The signal peptidase cleaves the preprogalanin at either Gly23 or Gly25.