NA-TRANSPORT IN RAT GASTRIC-MUCOSA - AN ELECTRON-MICROPROBE ANALYSIS

To identify and characterize the cells involved in Na absorption in th e mammalian stomach, the electrolyte concentrations of surface and gla nd cells were determined in isolated rat gastric mucosa using electron microprobe analysis. The isolated mucosa pieces were kept under resti ng (no H secretion) and short-circuited conditions. Na transport was i nhibited by amiloride and/or ouabain. The short-circuit current was re duced by about 65% by mucosal amiloride and to almost zero by ouabain. Whereas under control conditions normal electrolyte patterns with low Na and high K concentrations were found in surface and upper and lowe r gland cells, the cells of the middle gland zone exhibited high Na an d Cl and low K concentrations, probably caused by anoxic injury during chamber incubation. After inhibition of the Na-K pump by ouabain, sur face and intact (lower) gland cells showed a drastic increase in Na (f rom 41 to 103 in surface and from 16 to 120 mmol/kg wet weight in lowe r gland cells) and a decrease in K (from 120 to 58 in surface and from 145 to 41 mmol/kg wet weight in lower gland cells) concentrations. Th e concomitant increase in Cl concentration by about 16 mmol/kg wet wei ght and the fall in dry weight content by about 5 g/100 g wet weight i n both cell types indicate that ouabain induced cell swelling. Since p rior application of amiloride prevented the ouabain-induced Na increas e in surface but not in gland cells, only the surface cells seem to be involved in transepithelial Na transport. Without Na in the serosal s olution the Na concentrations in surface cells were relatively low und er all experimental. conditions and gland cells failed to increase the ir Na after ouabain. Surface cells thus seem to take up Na from both t he mucosal and serosal sides, whereas gland cells obtain their Na pred ominantly from the serosal side.