The expression of gastric H+-K+-ATPase mRNA and protein in developing rat fundic gland

The proton pump H+-K+-ATPase is the final common pathway mediating the prod uction and secretion of hydrochloric acid by gastric parietal cells. The pr esent studies were undertaken to examine whether the expression of gastric H+-K+-ATPase mRNA and protein changes are associated with the development o f H+-K+-ATPase activity in the rat fundic gland. H+-K+-ATPase activity was examined in rat fundic gland at different stages from gestational day 18.5 to postnatal 8 weeks. The expression of H+-K+-ATPase mRNA was detected by i n situ hybridization using a digoxigenin-labelled RNA probe with a tyramide signal amplification system. The expression of H+-K+-ATPase protein was ev aluated by immunoblotting and immunohistochemistry using antibodies against H+-K+-ATPase alpha- and beta -subunits. We found that H+-K+-ATPase enzyme activity was detectable from the onset of gland formation (day 19.5 of gest ation) and increased with age in the developing rat fundic gland. Expressio n of mRNA and protein was also discernible at the same time, and a progress ive increase in expressions was observed as rats developed. Our results sug gested that in developing rat fundic gland, the expression of both mRNA and protein of H+-K+-ATPase increased with age in a manner that parallels the development of H+-K+-ATPase enzymebreak activity.