To synthesize nitrosyl meso-tetrakis(4-aminophenyl)porphyrin cobalt (TAPP-Co-NO) as NO donor, the NO-releasing property of TAPP-Co-NO in aqueous solution was studied by diazotization at room temperature. Next, the relaxation of TAPP-Co-NO was investigated on isolated aorta pectoralis circle in the rabbit. Finally, eighteen rats were randomized into two groups. The treatment group was injected venously with 0.5 mL of TAPP-Co-NO mixed DMSO, and the control group was given with 0.5 mL of DMSO. The systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rates (HR) were measured before and after administration. NO-releasing ratio of TAPP-Co-NO was 63.17%. TAPP-Co-NO shifted methoxamine cumulative dose-response curves rightward im-paralleled and reduced the maximal response (E_max), the reduced percentage was 55.7%. For the treatment group, the blood pressure of rats began to decrease at the time of 5 s after the administration. The blood pressure of rats reached minimum at the time of 10 s, then increased gradually, and finally, approached normal blood pressure at 60 s. For the control group, the blood pressure of the rats was not changed after employing the DMSO. The results show that NO-releasing ratio of the TAPP-Co-NO was relatively high and it could decrease blood pressure instantaneously.

Key words: TAPP-Co-NO, NO donor, isolated vascular circle, depressurization