Abstract:Effects of nonylphenol (NP) on monoamine oxidase (MAO) activity and 5-hydroxytryptamine (5-HT) level of rats were investigated. The toxic mechanisms of NP on catabolism of 5-HT were also analyzed. 24 male SD rats were randomly divided into 4groups, namely NP low-dose group 30mg/(kg·bw), NP medium-dose group 90mg/(kg·bw), NP high-dose group 270mg/(kg·bw) and control group (equal volume of the solvent). NP in corn oil was administrated orally to rats once every other day for 28days, and rats in control group was only given corn oil. The increment of rat body weight in NP high-dose group was lower than that of control group (P<0.01). From the third week of exposure, significant differences were found for the food utilization rates, the liver, kidney and testis coefficients between treatment groups and control group (P<0.05, P<0.01, P<0.01, P<0.05). Compared with control group, significantly lower MAO activities of plasma and liver homogenate and higher 5-HT levels were observed in treatment groups (P<0.01, P<0.05, P<0.01). NP exposure has a dose-dependent effect on MAO activity and 5-HT level of rats, suggesting that NP may affect the metabolic network of 5-HT by inhibiting its catabolism.