Glucocorticoid effects on gastric peroxidase activity.
The peroxidase activity in rat gastric mucosa is inhibited after administration of glucocorticoids. The synthetic steroid dexamethasone is more potent than the naturally occurring steroids, such as cortisone or corticosterone. Almost complete inhibition of the enzyme occurs after 24 h with a single dose of 100 micrograms dexamethasone/120 g body weight. Other mitochondrial enzyme activities, like monoamine oxidase, succinic dehydrogenase and Mg2+-ATPase, remain unaltered under the same experimental condition. Submaxillary peroxidase and thyroid peroxidase activity are not inhibited by dexamethasone. Gastric peroxidase activity is increased 200-250% on the 6th day after adrenalectomy. This effect is blocked by the administration of dexamethasone. In fact, the enzyme becomes more sensitive to dexamethasone after adrenalectomy, since it is inhibited by more than 90% at the dose of 25 micrograms/120 g body weight. The inhibition by dexamethasone in normal animals is reversible. The enzyme is also inhibited after the administration of a single dose of ACTH. The apparent Km of the enzyme for H2O2 is not altered after dexamethasone treatment or after adrenalectomy. The increase in enzyme activity following adrenalectomy is not blocked by actinomycin D or by alpha-amanitin, but is prevented by puromycin or cycloheximide. After administration of dexamethasone, the iodide concentration process in the gastric mucosa is not affected, but the organification of iodide is significantly diminished.
D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D003345:Corticosterone / Q000494:pharmacology; D003348:Cortisone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005753:Gastric Mucosa / Q000201:enzymology*; D005938:Glucocorticoids / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology; D007454:Iodides / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats
D005938:Glucocorticoids; D007454:Iodides; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D010544:Peroxidases; D003348:Cortisone; D003345:Corticosterone; D006854:Hydrocortisone