“The protective … of S1P were reversed by the nitric-oxide synthase (NOS) inhibitor N-monomethyl-l-arginine , but not by the soluble guanylyl cyclase inhibitor 1H-(1,2,4)oxadiazolo[4,3-a]-quanoxaline-1-one, suggesting that NO, but not cGMP, is responsible for S1P protection from apoptosis.”