Reversible and potent uncoupling of hog gastric (H(+)+K(+))-ATPase by prodigiosins.
Prodigiosin, prodigiosin 25-C, and metacycloprodigiosin all strongly inhibited the acidification activity of (H(+)+K(+))-ATPase on membrane vesicles from hog gastric mucosa (IC(50) = 32 to 103 pmol/mg protein). But, the prodigiosins, unlike omeprazole, showed little inhibitory effect on K(+)-dependent ATPase (K(+)-ATPase) activity, although at higher concentrations they inhibited K(+)-ATPase activity with an IC(50) of 1.5 to 3.0 microM. Furthermore, the inhibitory effect of the prodigiosins was rapid and completely reversible unlike that of omeprazole, and the mode of inhibition was non-competitive with respect to ATP. Hog gastric (H(+)+K(+))-ATPase itself showed an absolute requirement of halide (effectively, chloride) for acidification activity. Prodigiosins also showed a chloride requirement for inhibition of vesicular acidification, and quickly reversed the acidification of vesicular pH to neutrality even in the presence of N, N'-dicyclohexylcarbodiimide (DCCD), showing their ionophoric nature of acidification inhibitory activity. In fact, tributyltin chloride (TBT, an OH(-)/Cl(-) exchange ionophore) also inhibited vesicular acidification, but it inhibited K(+)-ATPase activity too. Finally, the prodigiosins inhibited the acid secretion from parietal cells isolated from rabbit gastric mucosa. These results suggest that prodigiosins are potent reversible uncouplers of (H(+)+K(+))-ATPase that inhibit gastric acid secretion.
Matsuya
H
H
Laboratory of Biochemistry, Department of Molecular and Cellular Biology, Faculty of Pharmaceutical Sciences, Kanazawa University, 920-0934, Ishikawa, Japan.
Okamoto
M
M
Ochi
T
T
Nishikawa
A
A
Shimizu
S
S
Kataoka
T
T
Nagai
K
K
Wasserman
H H
HH
Ohkuma
S
S
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D009853:Omeprazole / Q000494:pharmacology; D011353:Prodigiosin / Q000494:pharmacology*; D054328:Proton Pump Inhibitors; D011817:Rabbits; D022142:Secretory Vesicles / Q000187:drug effects; D013552:Swine
D000900:Anti-Bacterial Agents; D002712:Chlorides; D004791:Enzyme Inhibitors; D054328:Proton Pump Inhibitors; D000255:Adenosine Triphosphate; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole; D011353:Prodigiosin