title: Electron microscopic radioautographic identification of the ECL cell as the histamine-synthesizing endocrine cell in the rat stomach.
abstract: Rat gastric oxyntic glands contain argyrophil "enterochromaffin-like" endocrine cells that synthesize and store histamine and also have APUD ability--they can take up exogenous L-5-hydroxytryptophan (5-HTP), can decarboxylate it to 5-hydroxytryptamine (5-HT, serotonin) by the enzyme DOPA-decarboxylase, and can store the amine. Previous cytochemical studies suggested that these cells correspond to both the ECL and A-like cells, the two predominant endocrine cells identified by electron microscopy (EM) in rat oxyntic glands. In a recent study, however, we demonstrated that the ECL but not the A-like cell exhibited APUD ability when rat gastric mucosa was incubated with H3-5-HTP and studied by EM radioautography. The purpose of the present study was to identify by EM radioautography the histamine-synthesizing endocrine cells in the rat stomach. Pieces of rat (male Sprague-Dawley) gastric mucosa were incubated in organ culture with L-H3-histidine (50 muCi, 1.8 x 10(-5) M) with and without inhibitors and were processed for LM and EM radioautography. H3-histidine labeled the ECL cells heavily but the A-like and other endocrine cells only lightly. The labeling of ECL cells was only modestly reduced by cycloheximide, an inhibitor of protein synthesis, whereas the labeling of A-like and other endocrine cells was almost abolished. In contrast, the labeling of ECL cells was markedly reduced by 4-bromo-3-hydroxybenzyloxyamine (NSD-1055), an inhibitor of histidine decarboxylase and DOPA decarboxylase, but was not appreciably affected by carbidopa, an inhibitor of only the DOPA decarboxylase. Incubations with H3-histamine (50 muCi, 0.9 x 10(-5) M) failed to label endocrine cells. Thus, this study demonstrates that the ECL but not the A-like cell is the histamine-synthesizing endocrine cell of the rat stomach.
mesh_terms: D001078:APUD Cells / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001345:Autoradiography; D001958:Brocresine / Q000494:pharmacology; D002230:Carbidopa / Q000494:pharmacology; D002838:Chromaffin System / Q000648:ultrastructure*; D003513:Cycloheximide / Q000494:pharmacology; D004759:Enterochromaffin Cells / Q000378:metabolism / Q000648:ultrastructure*; D005753:Gastric Mucosa / Q000378:metabolism / Q000648:ultrastructure*; D006632:Histamine / Q000096:biosynthesis*; D006639:Histidine / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000037:antagonists & inhibitors; D006651:Histocytochemistry; D007930:Leucine / Q000378:metabolism; D008297:Male; D014176:Protein Biosynthesis; D051381:Rats
chemical_list: D001958:Brocresine; D006639:Histidine; D006632:Histamine; D003513:Cycloheximide; D006640:Histidine Decarboxylase; D007930:Leucine; D002230:Carbidopa