Premium
Modulation of gastric H + , K + ‐transporting ATPase function by sodium
Author(s) -
Ray Tushar K.,
Nandi Joytirmoy
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)80733-x
Subject(s) - sodium , chemistry , physics , radiochemistry , organic chemistry
Gastric H + , K + ‐ATPase activity is not affected by Na + at pH 7.0 but is significantly stimulated by Na + at pH 8.5. For the stimulation at the latter pH, the presence of both Na + and K + were essential. Contrary the H + , K + ‐ATPase, the associated K + ‐pNPPase was inhibited by Na + at both pH values. Sodium competes with K + for the K + ‐pNPPase reaction. Also, unlike the H + , K + ‐ATPase activity the ATPase‐mediated transport of H + within the gastric microsomal vesicles was inhibited by Na + . For the latter event only the extravesicular and not the intravesicular Na + was effective. The data suggest that the K + ‐pNPPase activity does not represent the phosphatase step of the H + , K + ‐ATPase reaction. In addition, the observed inhibition of vesicular H + uptake by Na + appears to be due to the displacement by Na + of a cytosolic (extravesicular) H + site responsible for the vectorial translocation of H +