Altered expression of sodium transporters and water channels in the submandibular gland of rats treated with nitric oxide synthesis inhibitors.

A role of nitric oxide (NO) in the regulation of sodium transporters and water channels in the salivary gland was investigated. Male Sprague-Dawley rats were treated with N(G) -nitro-L-arginine methyl ester (L-NAME, 100 mg/L drinking water) for 1 week. The control group was supplied with normal tap water. The expression of Na(+),K(+)-ATPase, type 2 Na(+)/K(+)/2Cl(-) cotransporter (NKCC2), type 1 Na(+)/H(+) exchanger (NHE1), α-subunit of epithelial sodium transporter (ENaC), and aquaporin-5 (AQP5) and aquaporin-1 (AQP1) proteins were determined in the submandibular gland by Western blot analysis. Following the treatment with L-NAME, the expression of Na(+),K(+)-ATPase α1-subunit, NKCC2, NHE1, and ENaC α-subunit increased significantly. On the contrary, the expression of AQP5 was significantly decreased, while that of AQP1 was not significantly altered. These findings indicate that the sodium transporters and water channels may be under a tonic regulatory influence of NO in the salivary gland.