Induction of inducible nitric oxide synthase in hepatocytes isolated from rats with ischemia-reperfusion injury

Background. Recent evidence indicates that nitric oxide (NO) has a crucial role in hepatic ischemia-reperfusion (I/R) injury. However, little is known about how I/R influences the gene expression of inducible nitric oxide synthase (iNOS) in hepatocytes. Under inflammatory conditions, we compared the induction of iNOS in hepatocytes isolated from normal and I/R-treated rats. Methods. Hepatocytes were isolated using the collagenase perfusion method from rats treated with I/R (30-minute ischemia of middle and left lobes, followed by 3-hour reperfusion) or sham operation (control): Primary cultures of rat hepatocytes were incubated with an inflammatory cytokine, interleukin-1beta (IL-1beta), to compare the iNOS induction/NO production between the 2 groups. Results. Both control and I/R groups had no production of nitrite (a stable metabolite of NO) in the absence of IL-1beta. In the control group, IL-1beta stimulated dose- and time-dependent production of NO. The I/R group showed more than 2-fold increased levels of NO production. Western and Northern blot analyses revealed that the I/R group also showed increased levels of iNOS protein and its messenger RNA. Conclusion. These results suggest that I/R directly affects the inducibility of the iNOS gene in hepatocytes by IL-1beta. Increased NO may be associated with protective or toxic effects in hepatic I/R injury.