AIM: To explore the mechanism of the nitric oxide (NO) synthesis induced by human C5b-9 complex in glomerular mesangial cells(MC) of rats. METHODS: The MC of rats were cultured and stimulated with human complement C5b-9 complex to induce TNF? and IL-1?. At the same time, several parameters related to NO synthesis were measured at 3 h, 6 h and 24 h after C5b-9 stimulation. The effects of monoclonal antibodies against TNF? and IL-1? on NO synthesis were examined in this system. RESULTS: TNF? concentration in supernatant from MC in C5b-9 group was higher than that of control group at 6, 24 h after stimulation with C5b-9 complex and reversed by adding anti-TNF? McAb. C5b-9 complex didn't stimulate the release of IL-1? in same system. In addition, the expression of iNOS mRNA in MC was observed at 3 h after stimulation with C5b-9. Levels of iNOS mRNA expression and cGMP in MC and NO - 3/NO - 2 in supernatant from MC in C5b-9 group were higher than those in control group at 6, 24 h after C5b-9 stimulation, these changes were also reversed by adding monoclonal antibody against TNF?. CONCLUSION: C5b-9 complex could induce iNOS mRNA expression at 3 h after C5b-9 stimulation, and the synthesis of NO at 6, 24 h was related to TNF? released from cultured MC of rats by C5b-9 complex to a certain extent.

AIM: To explore the significance of measuring urinary complement C5b-9 complex in various types of immune complex (IC) nephritis models of rats. METHODS: The four models of rats, namely, passive Heymann nephritis (PHN), anti-thymocyte serum nephritis(ATSN), anti-glomerular basement membrane nephritis (AGBMN) and chronic serum disease nephritis (CSDN) were reproduced. Then, the contents of complement C5b-9 complex in plasma and urine of the rats were detected with sandwich ELISA. And the deposits of C5b-9 complex in glomeruli of the rats were examined by ABC immunohistochemistry staining. RESULTS: The contents of rat plasma C5b-9 were elevated and deposits of C5b-9 in glomeruli could be detected in the four model rats. But the increased urinary excretion of C5b-9 was observed only in PHN rats. Moreover, the time of urinary C5b-9 complex excretion was earlier than that of urinary protein in the rats with PHN. CONCLUSION: Urinary C5b-9 complex excretion could be taken as one of several sensitive immunologic parameters in diagnosing of PHN and in distinguishing PHN from other type of nephritis.