Threshold levels of extracellular L-arginine that trigger NOS-mediated ROS/RNS production in cardiac ventricular myocytes

In this study we aimed to determine the levels of external L-Arg that trigger ROS/RNS production in cardiac myocytes. To this goal, we used a two-step experimental design in which acutely isolated cardiomyocytes were loaded with the dye coelenterazine that greatly increases its fluorescence quantum yield in the presence of ONOO– and O2–. Cells were then exposed to different concentrations of extracellular L-Arg and changes in fluorescence were followed spectrofluorometrically. It was found that below a threshold value of ~100 µM, decreasing concentrations of L-Arg progressively increased ONOO–/ O2–-induced fluorescence, an effect that was not mimicked by d-arginine or l-lysine and was fully blocked by the NOS inhibitor l-NAME. These results can be explained by NOS aberrant enzymatic activity and provide an estimate for the levels of circulating L-Arg below which ROS/RNS-mediated harmful effects arise in cardiac muscle.

Source: AJP: Cell Physiology - February 7, 2017 Category: Cytology Authors: Ramachandran, J., Peluffo, R. D. Tags: RESEARCH ARTICLE Source Type: research