Cellular expression of the pepsinogen and gastric proton pump genes in the stomach of winter flounder as determined by in situ hybridization

The sites of pepsinogen synthesis and hydrochloric acid secretion were localized in the glandular stomach mucosa of winter flounder using in situ hybridization with gastric-specific, biotinylated antisense RNA probes for three genes: pepsinogen IIa, pepsinogen IIb and the alpha -subunit of the proton pump (H+/K+-ATPase). The spatial expression patterns of the pepsinogen IIa and IIb genes appeared to be the same, but they differed From that of the alpha -proton pump gene. The gastric gland cells contained transcripts (mRNAs) of all three genes, whereas the mucous neck cells and surface mucous cells contained transcript of the a-proton pump only. The expression of the pepsinogen IIa, pepsinogen IIb and alpha -proton pump gene in the same gastric gland cells indicates that these cells synthesize pepsinogens and secrete hydrochloric acid simultaneously and confirms that they are of the oxynticopeptic type. The presence of the alpha -proton pump mRNA in the mucous neck and surface mucous cells, shown here for the first time, indicates that these cells are capable of secreting hydrochloric acid. The physiological importance of hydrochloric acid secretion by these two cell types remains unknown. (C) 2001 The Fisheries Society of the British Isles.