Recovery from ischemic renal injury is accompanied by enhanced DNA synthesis and a typical immediate early (IE) gene response. These two processes occur in distinct cell populations, suggesting that the IE gene response does not serve a proliferative function directly. As cellular stress induces an IE response through activation of the stress-activated protein kinases (SAPK) that is not proliferative and can be inhibited by N-acetyl-L-cysteine (NAC), we determined whether the Jun NH2-terminal kinases (JNK), members of the SAPKs, are activated during ischemia and whether NAC administration reduces the IE response and/or the induction of JNK activity. NAC (6 mM/kg body wt) infused 1 h prior to and 1 h following renal ischemia reduced c-fos and c-jun expression by 50 and 70%, respectively. Ischemia increased JNK activity, and this increase was inhibited by NAC. NAC infused animals had a higher glomerular filtration rate at 1 day (NAC, 0.9 +/- 0.2, vs. control, 0.05 +/- 0.01 ml/min, P < 0.001) and 7 days (NAC, 2.0 +/- 0.1, vs. control, 1.2 +/- 0.1, P < 0.001) after the induction of ischemia. NAC did not reduce the extent of proximal tubule necrosis at 24 h after reperfusion but improved histological appearance of the kidney at 7 days. The mechanism by which NAC ameliorates the loss of renal function is unknown but may involve its general properties as an antioxidant or a possible interaction with NAC and NO. We conclude that the IE gene response of the kidney to ischemia reperfusion is a consequence of the stress-activated kinase pathway and that part of the response is deleterious to kidney function and cellular integrity.