Immunohistochemical localisation of pterin-4 alpha-carbinolamine dehydratase in rat peripheral organs

The bifunctional protein PCD/DCoH is both a pterin-4 alpha-carbinolamine de hydratase (PCD) involved in the recycling of tetrahydrobiopterin (BH4) and a dimerisation cofactor (DCoH) of the hepatic nuclear factor 1 alpha (HNF-1 alpha). An antiserum raised against rat PCD/DCoH was used to localise the protein in peripheral organs. In liver, all the hepatocytes but not the oth er cell types are immunoreactive. In kidney, the protein is prevalent in th e proximal and distal convoluted tubules. In adrenals, all the cells of the medulla are labelled. Positive nerve cells occur in myenteric ganglia of t he whole gastrointestinal tract and in the intestinal submucous ganglia. Ma ny positive endocrine cells are present in the epithelium. The immunoreacti vity is either cytoplasmic (hepatocytes, convoluted tubules of the kidney a nd part of the gastrointestinal endocrine cells) or prominently nuclear (ki dney collecting tubules, adrenals, intestinal neural plexuses and part of t he gastrointestinal endocrine cells). Our results show that PCD/DCoH is pre sent in cells expressing enzymes that use BH4 as a cofactor and/or HNF-1 al pha. In addition, PCD/DCoH is present in other cells, for example, neurons in the submucosal plexus. This fact and the prominent nuclear immunoreactiv ity found in all the positive cells derived from the neural crests argue in favour of a new, still unknown function for the protein.