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Fig. 6 | Respiratory Research

Fig. 6

From: Arginase impairs hypoxic pulmonary vasoconstriction in murine endotoxemia

Fig. 6

Hypothetical roles of arginase and arginase inhibition on HPV. a Arginase and nitric oxide synthase (NOS) compete for the common substrate L-arginine. b In healthy control mice, the arginase inhibitor norNOHA may shift L-arginine to NOS thereby increasing the level of NO that in turn attenuates HPV. c Endotoxemia increases expression of NOS2 and Arg1. NOS2-dependent S-nitrosylation may promote Arg1 expression and activity. Increased Arg1 may decrease L-arginine concentration locally. Low local arginine levels might promote NOS2 uncoupling and reactive oxygen species (ROS) production. Increased NO levels and redox imbalance impairs HPV. Upregulated Arg1 also potentially increases downstream products including L-ornithine and polyamines, which may also impair HPV. d Inhibition of arginase by norNOHA restores HPV by preventing NOS2 uncoupling and ROS production by shifting more L-arginine to NOS2 and decreasing polyamines

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