TNFα expression in fa/fa and ?/fa rats pre- and 1 h posttreatment with LPS (0.5 μg/g). (A) Total liver RNA was isolated from three distinct rats/group at each time point, reverse transcribed, and amplified with TNF-specific primers. PCR products were separated on nondenaturing agarose gels, transferred to nylon membranes, and visualized by hybridization with TNF-specific probes. (B) Serum TNF concentrations were evaluated by ELISA using rat recombinant TNFα as standard. In both males and females, TNF expression was greater in serum and liver at 1 h after LPS than at any other time point (0, 0.5, 6, or 24 h) evaluated.