Tumour necrosis factor α production by rat blood and itsex vivo pharmacological modulation

Rat blood was investigated as a suitable test system for the discovery of inhibitors of tumour necrosis factor α (TNFα) biosynthesis. Lipopolysaccharide (LPS) caused a concentration- and time-dependent stimulation of TNFα production by heparinised rat blood with peak levels (1000–5000 U/ml; L929 bioassay) at 6h. Bioactive material was neutralised with a polyclonal rabbit anti-murine TNFα antibody which cross-reacts with rat TNFα. Dexamethasone, pentoxifylline and denbufylline inhibited TNFα production with IC50s of 6.0±2.0 nM, 20.6±8.00 μM and 138.0 nM, respectively. When rats were dosed p.o. with dexamethasone or pentoxifylline or i.p. with denbufylline and 1.5h later TNFα production was assessedex vivo by LPS-stimulated blood, a dose-related inhibition of TNFα production occurred with ID50s of approximately 0.08, 250.0 and 5.0 mg/kg, respectively. These results demonstrate that rat blood provides a useful test system for the detection andex vivo evaluation of inhibitors of TNFα biosynthesis.