To determine the role of nitric oxide (NO) in rat liver transporter regulation, we investigated in precision-cut liver slices the effect of NO and peroxynitrite (ONOO(-)), a reaction product of NO with superoxide (O(2(-))), on mRNA levels of 13 influx and efflux transporters. To inactivate Kupffer cells (KCs), liver slices were prepared from rats treated with gadolinium chloride (Gd). Transporter mRNA levels were determined after incubation of untreated (normal-slices) and Gd-pretreated slices (Gd-slices) for 18 h with Spermine NONOate (SpNO), an NO donor, and SIN-1 (3-(4-morpholinyl) sydnonimine hydrochloride, SIN), a ONOO(-) donor. SpNO and SIN varied all transporter mRNA levels examined, except organic anion transporting polypeptide 1b2 (Oatp1b2/Oatp4). SpNO in normal-slices and SIN in Gd- and normal-slices generally decreased influx and increased efflux transporter transcription. In contrast, these effects were not observed in Gd-slices treated with SpNO. SpNO and SIN in normal-slices commonly decreased organic anion transporter 2 (Oat2) and increased multidrug resistance-associated protein 2 (Mrp2) transcription, but differentially regulated bile salt export pump (Bsep) and multidrug resistance protein 2 (Mdr2) transcription, the up-regulation by SpNO and the down-regulation by SIN. In addition, the induction of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta was not observed after incubation with SpNO or SIN. These findings suggest that NO and ONOO(-) play a role in the regulation of rat transporter transcription in hepatocytes, which communicate with KCs, in a proinflammatory cytokine-independent manner.