Inducibility of gamma-glutamyltransferase by dexamethasone in rat liver: relationship with the cytochrome P-450 content.

Gamma-glutamyltransferase (GGT) inducibility by dexamethasone (DEX) in rat liver decreased by about 95% within the first 14 days of life, while the liver content of cytochrome P-450 (P-450) increased by about 500%. Cobaltic Protoporphyrin IX (CPP), given on the 9th day of life, caused a temporary depression of the P-450 liver content, with maximal effects 3 and 4 days after the administration of CPP. GGT induction by DEX was significantly higher in CPP-treated rats than in untreated ones, with maximum induction coinciding with the maximal decrease of P-450. These effects were CPP dose-dependent