Abstracts
1997 Digestive Disease Week

Nitric oxide production by splenocytes is increased after bile duct ligation in the rat.

T Liu, JA Wargo, M Leong, DM Murasko, KU Kahng. Departments of Surgery and Microbiology & Immunology, Allegheny University of the Health Sciences, MCP Hahnemann School of Medicine, Philadelphia, PA.

Immunosuppression in the presence of biliary obstruction is well recognized. In previous studies we have demonstrated that BDL in the rat results in a macrophage-mediated diminished proliferative response of rat splenocytes to concanavalin A (Con A), a T cell mitogen. The purpose of this study was to determine the effect of BDL on splenocyte production of NO, a macrophage product that inhibits T cell function. Male Sprague-Dawley rats were either observed (NL), underwent sham operation (SO), or underwent bile duct ligation (BDL) under sodium pentobarbital anesthesia. Splenocytes were harvested eight days later and were incubated for 3 days with Con A 5µg/ml alone, or with L-NMMA (120 µM) or D-NMMA (120 µM). Supernatants were assayed for inorganic nitrite (NO_2-), a stable breakdown product of NO, using the Greiss assay. Data were analyzed by ANOVA and Tukey-Kramer and values are expressed as means +/- SD. [Figure 1 not available.]

NO_2- levels were three-fold higher in the BDL group compared to NL and SO (Figure 1). This effect was significantly inhibited by the addition of L-NMMA, a competitive inhibitor of nitric oxide synthase, but not D-NMMA, its biologically inactive stereoisomer (Figure 2[not available]). We conclude that BDL results in increased splenocyte production of NO. This elevation in NO may be a mediator of BDL-induced immunosuppression.