Abstract
Experiments were performed in a newly established mouse macula densa cell line (NE-MD) (Jpn J Physiol, 2005) to investigate whether metabolic acidosis may modulate the nNOS protein expression and activity. In the present study, NE-MD cells were incubated in the presence of furosemide (12 μM) for 2 hours with or without amiloride (or its analogue), an inhibitor of the Na+/H+ exchangers. The nNOS protein expression was analysed by Western blotting. L-arginine (Arg)-induced NO generation was measured by using an NO-sensitive electrode. Intracellular pH (pHi) of NE-MD cells was monitored by the BCECF assay. We found that both L-Arg-induced NO generation and furosemide-induced nNOS protein expression were significantly decreased by EIPA. Further, L-Arg-induced NO generation was significantly higher when NE-MD cells were incubated with low (1/10) Cl− solution, but not with low (1/10) Na+ solution. Moreover, L-Arg-induced NO generation was significantly lower at pH=7.1, compared with control (pH7.4). These results indicate that nNOS protein expression and activity may be sensitive to an acidic condition. In conclusion, low [Cl−] and acidic urine may increase and decrease, respectively, NO generation in NE-MD cells. [J Physiol Sci. 2007;57 Suppl:S130]
