Glutathione enhances endothelium-mediated control of coronary vascular resistance via a ROS- and NO intermediate-dependent mechanism.

The purpose of this investigation was to determine the effects of acute physiological GSH administration on endothelium-mediated reduction in coronary vascular resistance (CVR) using isolated perfused Sprague-Dawley rat hearts. A dose-response curve to GSH was conducted to determine a threshold concentration of GSH. We demonstrate that 30 μM GSH was sufficient to reduce CVR, and maximal dilation was achieved with 1 mM. In subsequent experiments, GSH was administered at concentrations of 0 [control (CON)], 1 μM, or 10 μM (GSH(10)), and dose-response curves to the endothelial agonist bradykinin (BK) were constructed. These GSH concentrations were chosen because of the physiological relevance and because the effects of GSH on BK action could be assessed independent of baseline differences in CVR. Sensitivity to BK (EC(50)) was enhanced in GSH(10) vs. CON (P < 0.05). This enhancement remained in the presence of nitric oxide (NO) synthase inhibition l-(ω)nitro-l-arginine (lNAME) and/or soluble guanylate cyclase (sGC) inhibition. Treatment with 4-hydroxy (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPOL) enhanced the sensitivity to BK in CON, similar to the effects of GSH(10) and GSH(10) + TEMPOL. However, the GSH(10)-dependent enhancement of EC(50) observed in the presence of lNAME did not occur in the presence of lNAME + TEMPOL or in the presence of lNAME + sGC inhibition and NO scavenging. Collectively, these results suggest that GSH enhances BK-mediated dilation and reduction in CVR through an antioxidant-dependent mechanism that involves a NO intermediate but is unrelated to acute production of NO and GC-dependent effects of NO. These results suggest a mechanism whereby physiologically relevant levels of GSH modulate the endogenous reactive oxygen species and NO control of endothelium-dependent coronary vascular function.