Development and application of an isolated perfused rat liver model to study the stimulation and inhibition of tumor necrosis factor-alpha production ex vivo.

Abstract

To develop an isolated perfused rat liver (IPRL) model with low baseline levels of tumor necrosis factor (TNF)-alpha in the outlet perfusate to study the effects of immunostimulants and immunosuppressants on the release of TNF-alpha from this organ. Isolated rat livers were perfused with a buffer containing no albumin or three different bovine serum albumin (BSA) preparations. Using the no-albumin perfusate, the inhibitory effects of methylprednisolone (MP) on lipopolysaccharide (LPS)-stimulated release of TNF-alpha were studied in livers isolated 1 or 5 h after the intravenous administration (5 mg/kg) of MP. The concentrations of TNF-a in the outlet perfusates were measured using enzyme-linked immunosorbent assay. In the absence of albumin, the perfusate levels of TNF-alpha were close to zero. However, when the perfusate contained BSA. the TNF-alpha levels in the perfusate reached as high as 1200 pg/ml at steady state. An injection of LPS into IPRLs perfused with a no-albumin perfusate resulted in mean (+/- SD) TNF-alpha steady-state concentrations of 825 +/- 125 pg/ml. The pretreatment of rats with MP before liver harvest attenuated the LPS-induced TNF-alpha release in the livers. However, the attenuation was substantial (>60%) and was statistically significant only 5 h after pretreatment with MP. Perfusates containing BSA may result in nonphysiologically high levels of TNF-alpha. An IPRL with a no-albumin perfusate is more suitable for studies of the stimulation and inhibition of TNF-alpha production by this organ.