On the basis of these findings, authors speculate that the normal CalvNO values militate against a generalized disorder of NO metabolism in PCD children, and hypothesize that NOS3 (endothelial) has normal function in PCD, while the uncoupling of the contractile process of the cilia from NOS2 (inducible) may result in failure of NO production. Here, NOS3 is linked to primary ciliary dyskinesia.