Shear stress-mediated NO production in inner medullary collecting duct cells

Recent evidence suggests that nitric oxide (NO) within the inner medullary collecting duct (IMCD) functions to regulate sodium and water reabsorption. Because fluid shear stress has been shown to increase NO production in end othelial and vascular smooth muscle cells, experiments were designed to det ermine whether a similar mechanism exists in IMCD cells. Cultured IMCD-3 ce lls derived from murine IMCD were subjected to 60 min of pulsatile shear st ress. Nitrite production (2,3-diaminonaphthalene fluorometric assay) increa sed 12-, 16-, and 23-fold at 3.3, 10, and 30 dyn/cm(2), respectively, compa red with static control cultures. Preincubation with the non-isoform-specif ic NO synthase inhibitor nitro-L-arginine methyl ester reduced nitrite prod uction by 83% in response to 30 dyn/cm(2). Western blotting and immunofluor escence analysis of static IMCD-3 cell cultures revealed the expression of all three NO synthase isoforms (NOS-1 or neuronal NOS, NOS-2 or inducible N OS, and NOS-3 or endothelial NOS) in IMCD-3 cultures. These results indicat e that NO production is modulated by shear stress in IMCD-3 cells and that fluid shear stress within the renal tubular system may play a role in the r egulation of sodium and water excretion by control of NO production in the IMCD.