Alteration by cadmium of rat submandibular gland secretory function and the role of the L-arginine/nitric oxide pathway

The effects of cadmium, L-arginine (nitric oxide precursor) and NO-nitro-L-arginine methyl ester (L-NAME) as a nitric oxide synthesis inhibitor and cotreatment of them on rat submandibular secretory function were studied. Pure submandibular saliva was collected intraorally by micro polyethylene cannula from anaesthetized rats using pilocarpine as secretagogue. Fourteen days treatment with 10 mg l(-1) cadmium as cadmium chloride in drinking water caused significant alterations on salivary function. Salivary flow rate, total protein concentration and amylase activity of saliva were decreased while secretion of calcium was increased by cadmium. Two weeks treatment of rats with L-arginine (2.25%) in drinking water caused an increase in submandibular gland weight. Flow rate was reduced by L-NAME. The total protein concentration of saliva was increased by L-arginine while decreased by L-NAME. Calcium concentration of saliva was reduced by L-arginine and increased by L-NAME. Cotreatment of cadmium with L-arginine prevented cadmium-induced reduction of flow rate while L-NAME cotreatment potentiated cadmium-induced reduction of flow rate. L-arginine showed a preventive effect on cadmium-induced decrease of protein concentration and reached control levels. L-arginine potentiated cadmium-induced increase of saliva calcium concentration. It is confirmed that nitric oxide (NO) has a role in salivary gland function. It is also concluded that cadmium inhibitory effects on salivary gland function are modulated by the NO system as it is observed that the cadmium inhibitory effect on submandibular gland function is diminished by L-arginine and extended by L-NAME. Considering the properties of cadmium substitution for calcium in many intracellular events, different types of alterations can be discussed. (C) 2000 Academic Press.