Paraquat cytotoxicity to murine fibroblasts is enhanced by endogenous and exogenous production of nitric oxide: WR Berrington, BR Pitt, E Tzeng, and BA Freeman. Depts Anesthesiology, Biochemistry and Molecular Genetics, and the UAB Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL; Depts of Pharmacology and Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA