Fluoride causing abnormally elevated serum nitric oxide levels in chicks.

Serum fluoride, nitric oxide (NO), malondialdehyde (MDA) contents and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities were determined in chicks treated with graded doses of sodium fluoride. Compared with chicks in the control group, in the groups treated with fluoride, serum NO and MDA levels largely increased, and the activities of SOD, GSH-Px, and CAT decreased, most of which changed significantly (P<0.05). Serum fluoride levels significantly and positively correlated with serum NO, MDA levels, respectively (P<0.05), and significantly and negatively with serum SOD, GSH-Px, CAT activities, respectively (P<0.05). The results indicated fluoride was associated with the elevated NO levels and the decreased activities of antioxidant enzymes and the deposit of lipid peroxides (LPO). We suggest the mechanism of fluoride injuring soft tissues as follows: fluoride causes excessive production of NO, LPO and oxygen free radicals, which can damage seriously the structure and function of soft tissues.