An Improved Assay for Measuring Low Levels of Nitric Oxide in Cultured Pulmonary Myofibroblasts

Abstract

Quantification of nitric oxide (NO) from cultured cells is a valuable tool for studying cell signaling. Detection of NO in biological fluids can be difficult however, due to its transient half-life and low physiological concentrations. In this study, we have refined an existing amperometric method to determine relative levels of accumulated nitrogen oxides (NO X) in cell culture and have used this method to reproducibly quantify NO from cultured pulmonary myofibroblasts. Basal levels of NO produced by pulmonary myofibroblasts ranged from 0.6 nM to 20 nM and varied due to the growth conditions of the cells, i.e. higher NO concentrations were observed in differentiated cells. The constitutive eNOS isoform is primarily responsible for the observed NO accumulation in these cells since transcript levels of eNOS are 10-fold higher than the inducible iNOS form while nNOS was undetectable. Treatment of myofibroblasts with the inhibitors L-NNA and L-NAME resulted in a concentration dependent decrease in measured NOx. Overall, the improved assay presented here should be applicable to measuring NOX levels from many different cell types and under a wide variety of conditions.