Submitted on September 4, 2007
Accepted on November 12, 2007
Role of Cu,Zn-SOD in the Synthesis of Endogenous Vasodilator Hydrogen Peroxide during Reactive Hyperemia in Mouse Mesenteric Microcirculation in Vivo
Toyotaka Yada1*, Hiroaki Shimokawa2, Keiko Morikawa3, Aya Takaki4, Yoshiro Shinozaki5, Hidezo Mori6, Masami Goto7, Yasuo Ogasawara7, and Fumihiko Kajiya7
1 Department of Medical Engineering and Systems Cardiology, Kawasaki Medical School, Kurashiki, Japan
2 Dept of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
3 Anesthesiology, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
4 Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
5 Physiology, Tokai University School of Medicine, Isehara, Japan
6 Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Japan
7 Medical Engineering and Systems Cardiology, Kawasaki Medical School, Kurashiki, Japan
* To whom correspondence should be addressed. E-mail: yada{at}me.kawasaki-m.ac.jp.
We have recently demonstrated that endothelium-derived hydrogen peroxide (H2O2) is an endothelium-derived hyperpolarlizing factor (EDHF) and that endothelial Cu,Zn-superoxide dismutase (SOD) plays an important role for the synthesis of endogenous H2O2 in both animals and humans. We examined whether SOD plays a role in the synthesis of endogenous H2O2 during reactive hyperemia (RH), an important regulatory mechanisms, in vivo. Mesenteric arterioles from wild-type and Cu,Zn-SOD-/- mice were continuously observed by a pencil-type CCD intravital microscope during RH (reperfusion after 20 and 60 sec of mesenteric artery occlusion) in the cyclooxygenase blockade under the following 4 conditions; control, catalase alone, L-NMMA alone, and L-NMMA+catalase. Vasodilatation during RH was significantly decreased by catalase or L-NMMA alone, and was almost completely inhibited by L-NMMA+catalase in wild-type mice, whereas it was inhibited by L-NMMA and L-NMMA+catalase in the Cu,Zn-SOD-/- mice. RH-induced increase in blood flow after L-NMMA was significantly increased in the wild-type mice, whereas it was significantly reduced in the Cu,Zn-SOD-/- mice. In mesenteric arterioles of the Cu,Zn-SOD-/- mice, tempol, an SOD mimetic, significantly increased the ACh-induced vasodilatation, and the enhancing effect of tempol was decreased by catalase. Vascular H2O2 production by fluorescent microscopy in mesenteric arterioles after RH was significantly increased in response to ACh in wild-type mice but were markedly impaired in Cu,Zn-SOD-/- mice. In vivo observation using a pencil-type CCD intravital microscope revealed that endothelial Cu,Zn-SOD plays an important role for the synthesis of endogenous H2O2 that contributes to RH in mouse mesenteric smaller arterioles.
