Peptidylglycine alpha-amidating monooxygenase (PAM) immunoreactivity and messenger RNA in human pituitary and increased expression in pituitary tumours

Cell Tissue Res. 1994 Apr;276(1):197-207. doi: 10.1007/BF00354800.

Abstract

Bioactivity of many peptides depends upon post-translational alpha-amidation of inactive precursors by two enzyme activities known collectively as peptidylglycine alpha-amidating monooxygenase (PAM). PAM enzymes are particularly abundant in the pituitary. The distribution of PAM immunoreactivity and messenger ribonucleic acid (mRNA) in the adult human pituitary and in pituitary tumours was investigated by use of immunocytochemistry and in situ hybridisation. Immunoreactivity was present in numerous cells of the anterior lobe: staining was intense in a proportion of gonadotrophs and folliculo-stellate cells, but weaker in the majority of somatotrophs and lactotrophs, a few corticotrophs and occasional thyrotrophs. PAM staining was also present in nerves, pituicytes and some endocrine cells within the posterior lobe (the human intermediate zone). Forty pituitary tumours of various types were immunoreactive for PAM; more intensely and uniformly stained than normal anterior lobe. In situ hybridisation with digoxigenin-labelled probes demonstrated intense labelling for PAM mRNA in numerous cells in normal anterior pituitary and in tumours. Many regulatory peptides that require amidation for activity, potential targets for PAM, are present in the pituitary. Many tumour growth factors also require amidation and PAM may regulate these mitogenic peptides in tumours.

MeSH terms

  • Female
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization
  • Male
  • Mixed Function Oxygenases / analysis*
  • Mixed Function Oxygenases / genetics*
  • Mixed Function Oxygenases / physiology
  • Multienzyme Complexes*
  • Pituitary Gland / chemistry*
  • Pituitary Gland / cytology
  • Pituitary Gland / enzymology*
  • Pituitary Neoplasms / chemistry*
  • Pituitary Neoplasms / enzymology*
  • Pituitary Neoplasms / pathology
  • RNA, Messenger / analysis*
  • RNA, Messenger / genetics

Substances

  • Multienzyme Complexes
  • RNA, Messenger
  • Mixed Function Oxygenases
  • peptidylglycine monooxygenase