Hyperoxia-exposure results in neutrophil accumulation and edema in the exposed lung. Intercellular adhesion molecule-1 (ICAM-1), a ligand for neutrophil beta 2 integrins, is upregulated in hyperoxia-exposed lungs and enhances neutrophil-mediated injury. Because tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) are potent inducers of ICAM-1, we investigated whether TNF-alpha and IL-1 beta mRNA increase prior to the increase in ICAM-1 mRNA in hyperoxia-exposed mouse lungs. We exposed mice to > 95% oxygen for up to 96 h, isolated lung RNA, and assessed ICAM-1, TNF-alpha, and IL-1 beta mRNA by Northern blotting. We found that neither, TNF-alpha nor IL-1 beta mRNA was detectable prior to 96 h, while ICAM-1 mRNA increased by 48 h. To further assess TNF-alpha and IL-1 beta mRNA, we employed quantitative reverse-transcriptase polymerase chain reaction (RTPCR) using a mimic DNA (mimic) species as an internal control for PCR. Mimic DNA was identical to reverse-transcribed cDNA (wild type), except for 147 bp of irrelevant DNA ligated into the original cDNA. For each lung RNA sample we reverse transcribed total lung RNA and coamplified the resulting wild-type cDNA with serial dilutions of mimic DNA in a PCR containing [32P] dCTP. After PCR, we electrophoresed the samples and determined the concentration of TNF-alpha and IL-1 beta wild-type cDNAs by the ratios of wild type to mimic counts. We found no increase in TNF-alpha or IL-1 beta mRNA through 72 h of hyperoxia exposure, while there was an approximately 10-fold increase in TNF-alpha mRNA and a 35-fold increase in IL-1 beta mRNA within 2 h in the lungs of animals exposed to endotoxin. In conclusion, our data suggest that TNF-alpha and IL-1 beta are not responsible for the upregulation of ICAM-1 in hyperoxia-exposed mouse lungs.