Localization of gastric peroxidase and its inhibition by mercaptomethylimidazole, an inducer of gastric acid secretion.
Mercaptomethylimidazole (MMI) is a potent inducer of gastric acid secretion which is associated with significant inhibition of peroxidase activity of rat gastric mucosa in vivo. A time-dependent increase in acid secretion correlates well with time-dependent decrease in the peroxidase activity. In a chamber experiment in vitro using isolated gastric mucosa, MMI stimulates acid secretion, showing an almost linear response up to 600 microM. The time-dependent increase in acid secretion is also correlated with time-dependent inhibition of the peroxidase activity. This effect is not mediated through oxidation of MMI by flavin-containing mono-oxygenase, which is absent from gastric mucosa. The peroxidase has been localized mainly in parietal cells isolated and purified from gastric mucosa by controlled digestion with collagenase followed by Percoll-density-gradient centrifugation. Peroxidase activity was further localized in the outer membrane of the purified mitochondria of the parietal cell by some membrane-impermeant reagents, indicating outward orientation of the enzyme. MMI can inhibit the peroxidase activity of both the parietal cell and its mitochondria in a concentration-dependent manner. The possible involvement of the parietal-cell peroxidase-H2O2 system in MMI-induced acid secretion may be suggested.
Bandyopadhyay
U
U
Department of Physiology, Indian Institute of Chemical Biology, Calcutta.
Bhattacharyya
D K
DK
Chatterjee
R
R
Banerjee
R K
RK
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002458:Cell Fractionation; D005744:Gastric Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D008297:Male; D008713:Methimazole / Q000494:pharmacology*; D008928:Mitochondria / Q000201:enzymology; D010100:Oxygen / Q000378:metabolism; D010295:Parietal Cells, Gastric / Q000201:enzymology; D010544:Peroxidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000632:Aminopyrine; D008713:Methimazole; D002731:4-Chloromercuribenzenesulfonate; D006632:Histamine; D002217:Carbachol; D010544:Peroxidases; D010100:Oxygen