Table 2

Isoforms of NOS

	Endothelial NOS (eNOS)^2-a(Type III NOS, NOS-3)	Neuronal NOS (nNOS)^2-a(Type I NOS, NOS-1, bNOS)	Inducible NOS (iNOS)^2-a(Type II NOS, NOS-2, macNOS, hepNOS)
Primary regulation	Ca²⁺/calmodulin	Ca²⁺/calmodulin	Gene expression
Subcellular location	Membrane ≫ cytosol	Cytosol?	Cytosol ≫ membrane
NO output^2-b	Low (pmolar)	Low (pmolar)	High (μmolar)
Function	Cell signaling	Cell signaling	Cytotoxic
			Cytostatic
			Cytoprotective

↵2-a Previously used alternative abbreviation.
↵2-b All three isolated purified isoforms of NOS have comparable specific activities. Output in this case refers to differences in levels of enzyme expression and in duration of activation in the in vivo situation.