NO production and mtNOS kinetic parameters in kidney, liver and brain.

ALVAREZ, S.; VALDEZ, L.B.; LORES ARNAIZ, S.; BOVERIS, A.

New Orleans

Congreso; 6th Annual Meeting of The Oxygen Society; 1999

The Oxygen Society

Nitric oxide (NO) is produced by the oxidation of L-arginine to L-citrulline in the presence of NADPH and O2. This reaction is catalized in vivo by a multitude of nitric oxide synthases (NOS): neuronal NOS, endothelial NOS and inducible NOS. Recently the presence of a NOS (mtNOS) associated to the inner mitochondrial membrane, has been reported. The aim of this work was to study the NO production by mitochondria of different rat organs at several pO2, and to calculate the Km and vmax of mtNOS for O2. The brain mtNOS was the most sensitive of the isoforms studied, to pO2 variations, producing 0.590 nmol/min.mg prot (control value: 0.091 nmol NO/min.mg prot) at 260 uM. The Km and vmax for the enzyme were: a) liver: 10.3 uM and 0.477 nmol NO/min. mg prot, b) brain: 75.3 uM and 0.685 nmol/min.mg prot, and c) kidney: 17.8 uM and 0.284 nmol/min.mg prot. This result give new insights to the study of the regulation of NO production by mitochondria.