IRS-2 inhibits carrageenan-induced acute inflammation. Mice received carrageenan injections intraplantary in either the absence or presence of 0.3 or 1 mg/kg IRS-2. (A) Edema formation was evaluated at 4 and 24 hours after injection (abscissa) as the increase in paw thickness (in millimeters). (B) Neutrophil recruitment in inflamed footpads was evaluated by measuring tissue myeloperoxidase activity, expressed as units of activity/g of tissue (ordinate). Bar 1 (numbering left to right), activity detected when only carrageenan was administered to mice; bars 2 and 3, effect of coadministration of carrageenan with 0.3 and 1 mg of IRS-2 per 1 kg of body weight, respectively. Bar 4, IRS-2 injected without carrageenan. (C) Mice received injections of saline (-), carrageenan, carrageenan plus IRS-2 (1 mg/kg), indomethacin (0.3 and 1 mg/kg) or chymostatin (0.3 and 1 mg/kg). At 4 hours after injection, the hind paws were collected for MPO analysis and the amount of neutrophils per milligram of tissue was estimated by comparison with purified neutrophils. Asterisks represent statistically significant differences in MPO activity (*P < .05; **P < .01; and ***P < .001), compared with groups injected with carrageenan only (1-way analysis of variance followed by Tukey post-hoc test; n:4 in each group).