Nitric oxide (NO) in renal physiology and pathophysiology.

Endogenous NO is synthesized by nitric oxide synthases (NOS) which use L-arginine as substrate. The various isoforms of NOS are widely distributed within the kidney. Brain NOS (bNOS) and endothelial NOS (eNOS) are constitutively expressed and are both distributed in glomeruli and vasculature. In addition bNOS is found in epithelial tissue including macula densa and the collecting duct. Two structurally distinct inducible NOS (iNOS) are 'constitutively expressed' at the juxtaglomerular apparatus (JGA) and in tubules and after immune stimulation iNOS has been located in glomerular mesangial cells and several locations in the tubule [1,2]