In vivo time-dependent expression of CAT in response to dexamethasone (Dex) after administration of the AdGRE.CAT vector. CAT activity in the liver was evaluated before and 1 to 14 days after intravenous administration of the vector to C57B1/6 mice. (A) Time-dependent expression of CAT following administration of the AdGRE.CAT vector and dexamethasone. AdGRE.CAT (5 × 10⁸pfu) was administered intravenously and dexamethasone and (50 μg) was administered intraperitoneally at day 1. Shown are data for CAT expression with dexamethasone (•) or without dexamethasone (○). (B) Effect of multiple daily administration of dexamethasone on CAT expression after administration of the AdGRE.CAT vector. The vector administration was identical to (B), but dexamethasone (50 μg/d) was administered intraperitoneally on 6 consecutive days. (C) Time-dependent expression of CAT following intravenous administration of AdGRE.CAT (5 × 10⁸ pfu; ○) or AdRSV.CAT (5 × 10⁸ pfu; ▵); no dexamethasone was administered. Shown are data for AdGRE.CAT after 6 days' administration of dexamethasone (▴) or without dexamethasone (○). The data are presented as mean ± SE of three independent experiments.