Abstract: Aim Export of mRNA from nucleoplasmic space via the nuclear pore complex requires nuclear nucleoside triphosphatase (NTPase) activation. It is widely believed that taurine plays important role in protecting cells from toxic injury by functioning as an antioxidant. To investigate whether taurine can directly protect nuclei NTPase from HOCl induced damage, the effects of taurine on NTPase due to incubation with HOCl were studied. Methods Isolated hepatic nuclei from rat liver were exposed to HOCl with or without taurine. The NTPase activities on nuclei were assayed using ATP and GTP as substrates. Results Incubation of rat hepatic nuclei with HOCl (1×10-9-5×10^-6 mol·L^-1) resulted in a concentration dependent decrease in nuclear NTPase activity (P<0.01). The reduction of NTPase activities induced by HOCl (1×10^-6 mol·L^-1) was antagonized by taurine from the very low concentration of 1×10^-6 mol·L^-1 (for ATP and GTP as substrates) (P<0.01). In incubating the nuclei with HOCl (1×10^-6 mol·L^-1) and taurine (5×10^-4 mol·L^-1), the nuclear NTPase activities reached (102±14) nmol·mg^-1(protein)·10 min^-1 (for ATP as substrate) and (133±12) nmol·mg^-1(protein)·10 min^-1 (for GTP as substrate), which showed significant differences from that of incubating the nuclei with HOCl alone ［(44±5) and (36±4) nmol·mg^-1(protein)·10 min^-1］ (P<0.01). In addition, incubation of hepatic nuclei with taurine (1×10^-6-1×10^-4 mol·L^-1) slightly increased the nuclear NTPase activity, as compared with that of the control group (P<0.01), indicating that taurine itself showed NTPase-stimulating effect. Conclusion These data demonstrate that taurine antagonistically attenuated the toxicity of HOCl to the NTPase, indicating that nuclear NTPase would be one of the favorable targets of OCl- and taurine protects nuclear NTPase.