Participation of nitric oxide synthase and cyclooxygenase-2 in the salivary secretion of hypothyroid endotoxemic rats

Abstract

Purpose: In the present study the participation of nitric oxide synthase (NOS) and cyclooxygenase-2 (COX-2) on salivary secretion in endotoxemic hypothyroid rats was investigated. Methods: Male Wistar rats with an initial weight of 180 g were distributed into two groups, normal (N) or treated with propylthiouracil, 0.05 g/100 mL, administered orally for 5 weeks to induce hypothyroidism. Both groups were treated with lypopolysaccharide (LPS) (2.5 mg/kg; i.p.) to induce endotoxemia, or saline solution (SL), 90 min before salivary stimulation with pilocarpine (5 mg/kg; i.p.). Normal and PTU rats were divided into two groups each (n=07/09), receiving either L-NAME (10 mg/kg; i.p.), NOS inhibitor, or meloxicam (MLX) (0.5 mg/kg; i.p.), preferential COX-2 inhibitor, 30 min before endotoxemia challenge. Saliva was collected over a 15 min period (μL/min/100 g body wt.) from the time of the first drop of saliva. Results: Hypothyroidism decreased salivary flow rate in both groups of rats (LPS and SL). Endotoxemia and NOS inhibition by L-NAME reduced salivary flow in N rats. Meloxicam stimulated salivary secretion in the physiological state and systemic inflammation, induced by LPS, in N and PTU rats (Mann-Whitney Test; P < 0.05). Conclusion: In hypothyroid endotoxemic rats, it is COX-2 that modulates salivary secretion, not NOS.