Tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) mediate in part the microbicidal response of murine and rodent alveolar macrophages (AM) and recruited neutrophils (PMN) to airborne infections. Ethanol (ETOH) suppresses intrapulmonary TNF alpha and NO release and impairs pulmonary host defense mechanisms. We tested the concept that ETOH down-regulates NO by inhibiting production of TNF alpha. Male rats were given intratracheal (i.t.) saline (PBS), a polyclonal anti-TNF alpha antibody (TNFab) or nonimmune IgG (22 mg/kg, i.m.) 2 h before giving i.t. Escherichia coli endotoxin (LPS) to normal rats or rats pretreated with ETOM (5.5 g/kg, i.p.) 30 min before experimentation. AM and PMN were obtained from the bronchoalveolar lavage fluid (BAL) fluid of rats killed 2 and 4 h after administration of LPS. mRNA for inducible NO synthase (iNOS) and TNF alpha were measured in AM and PMN with competitor equalized RT-PCR techniques. The BAL fluid, AM, and PMN were assayed for TNF alpha and NO2-, and NO3- (RNI) with the L929 bioassay and chemiluminescence, respectively. TNFab abolished LPS-induced increases in TNF alpha but did not suppress the NO content of the BAL fluid or gene expression for iNOS by AM or PMN. ETOH suppressed LPS-induced increases in mRNA for iNOS, production of RNI, and BAL fluid TNF alpha but did not affect LPS-induced increases in mRNA for TNF alpha. ETOH-induced attenuation of LPS-induced up-regulation of the iNOS system did not differ in rats pretreated with TNFab or IgG. Thus, ETOH down-regulates iNOS gene expression and RNI production independent of its effects on TNF alpha. Acute ETOH administration suppresses iNOS at the level of transcription and TNF alpha at the level of translation or release of the peptide.