抄録
Kidney macula densa cells sense the chloride concentration of the fluid in the adjacent lumen and control glomerular filtration rate. We have used a functionally intact macula densa cell line (NE-MD) established from immortalized renal cells in culture. NE-MD cells specifically express neuronal nitric oxide synthase (nNOS) regulated by either low NaCl intake or furosemide (an inhibitor of Na+-K+-2Cl− symporter). We have examined whether L-arginine-induced NO production is pH dependent or not in NE-MD cells, by using a NO-sensitive electrode. The NO production was low in control, but increased when NE-MD cells were treated with furosemide (12 µM) for 2 hrs. When furosemide-treated NE-MD cells were incubated in the presence of 100 μM amiloride (an inhibitor of Na+/H+ exchanger), L-arginine-induced NO production was unaffected. However, the NO production significantly decreased by 42% when the cells were placed in a solution containing amiloride. Similar results were obtained when NE-MD cells were incubated in the low pH solution (pH=7.1). These results strongly suggest that furosemide-induced expression of nNOS protein is not sensitive to acidosis, but its activity is pH sensitive. This may partly account for polyuria in abnormalities of electrolyte and acid-base balance. [J Physiol Sci. 2006;56 Suppl:S140]
