Abstract: 　Objective To explore whether NO is able to induce apoptosis in Toxoplasma gondii tachyzoites.Methods Apoptosis induced by NO in T.gondii tachyzoites was investigated by TUNEL (terminal-deoxynucleotidyl transferase mediated d-UTP nick end labeling ) method, electron microscopy and agarose gel electrophoresis. Results NO donor, sodium nitroprusside (SNP),was found to induce apoptosis in Toxoplasma gondii tachyzoites in a time- and dose-dependent manner by TUNEL detection. N-acetylcysteine, a NO scavenger, could inhibit SNP-induced apoptosis in the tachyzoites while potassium ferricyanide could not induce apoptosis in the tachyzoite. Electron macroscopy showed that SNP-treated tachyzoites possessed typical morphological features of apoptosis, including chromatin condensation below the nuclear membrane, nuclear pyknosis, and formation of apoptotic body.Agarose gel electrophoresis revealed that SNP-treated tachyzoite DNA fragment exhibited characteristic "DNA ladder" after 15 to 20 h. Conclusion SNP, NO donor, might induce apoptosis in T.gondii tachyzoites in terms of characteristic morphological and biochemical features.

Key words: nitric oxide, Toxoplasma gondii, apoptosis