Localization of the Histamine H2-Receptor and Gene Transcripts in Rat Stomach: Back to Parietal Cells
Unité de Neurobiologie et Pharmacologie (U. 109) de l'INSERM, Centre Paul Broca, Paris, France.Biochemical and Biophysical Research Communications (Impact Factor: 2.3). 03/1994; 198(3):1195-202. DOI: 10.1006/bbrc.1994.1169
In contrast with many physiological studies suggesting that histamine H2 receptors are present on acid-secreting parietal cells of the gastric epithelium, it was recently shown that immune cells in the lamina propria are the only cells expressing H2-receptor mRNAs (Mezey and Palkovits, Science, 1992, 258, 1662-1665). We have reinvestigated the cellular localization of H2 receptors in the rat stomach by visualizing both the H2 receptor mRNA and the H2-receptor protein itself. In situ hybridization histochemistry performed with an antisense riboprobe for the rat H2 receptor, and autoradiographic distribution of 125I-aminopotentidine binding sites, a highly selective H2-receptor ligand, did not show any labeling of the lamina propria. Signals were clearly and solely detected in the gastric epithelium, the strongest being observed in the upper part of the glands where the H2 receptor gene transcripts were only detected within parietal cells. In situ hybridization performed with an antisense riboprobe for L-histidine decarboxylase mRNA confirmed the basal localization of the histamine-synthetizing cells in the rat gastric gland, at some distance from parietal histamine-sensitive cells.
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ABSTRACT: The human histamine H2 receptor gene (a 13 kb 5'-upstream sequence, the 1,077 bp coding region and a 245 bp 3'-downstream sequence) was cloned and its 5'-upstream 1.8 kb nucleotide sequence was determined. Northern blot hybridization showed that the message for the receptor was transcribed in human gastric adenocarcinoma MKN45 cells. When the upstream sequence was ligated in front of the luciferase gene and the construct was introduced into this cell line, the reporter gene was effectively transcribed, as demonstrated by the expression of enzyme activity. The minimum promoter was located in the region between -610 and -278. This sequence contained AP2 sites and GATA motifs, but not a TATA-box like sequence. Further upstream regions (-1,202 approximately -611 bp and -1,773 approximately -1,203 bp) stimulated and inhibited luciferase gene expression, respectively. These regions may be important for modulation of the mRNA level in cells expressing the H2 receptor.
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ABSTRACT: The guinea pig is the prototypic animal species for the histamine H2 receptor. Using a strategy based upon nucleotide sequence homology and starting from the sequence of the rat histamine H2 receptor (Ruat et al., Biochem. Biophys. Res. Commun. 1991, 179: 1470-78), we have cloned an intronless highly homologous DNA very likely encoding the guinea pig H2 receptor. The encoded 359 amino acid protein displays 83 to 86% identity with the rat-, human- or dog-H2 receptors. Northern blot analysis identified a single transcript of 4.6 kb in peripheral tissues and brain areas in which the presence of the H2 receptor had been revealed previously by either photoaffinity labeling or binding studies. In brain, the distribution of transcripts, established by either Northern blots or in situ hybridization studies, was consistent with the localization of the H2-receptor. In addition, using Southern analysis of a chromosome mapping panel constructed from human x hamster hybridomas, we assigned the H2 receptor gene to human chromosome 5.
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