Hydrogen sulfide downregulates the aortic L-arginine/nitric oxide pathway in rats

1 Institute of Cardiovascular Research, First Hospital of Peking University; 2 Department of Physiology, Peking University Health Science Center; and 3 Department of Pediatric, First Hospital of Peking University, Beijing, People's Republic of China Submitted 22 March 2006 ; accepted in final form 27 June 2007 The aim of the present study was to investigate the effect of hydrogen sulfide (H 2 S) signaling by nitric oxide (NO) in isolated rat aortas and cultured human umbilical vein endothelial cells (HUVECs). Both administration of H 2 S and NaHS, as well as endogenous H 2 S, reduced NO formation, endothelial nitric oxide synthase (eNOS) activity, eNOS transcript abundance, and L -arginine ( L -Arg) transport (all P < 0.01). The kinetics analysis of eNOS activity and L -Arg transport showed that H 2 S reduced V max values (all P < 0.01) without modifying K m parameters. Use of selective NOS inhibitors verified that eNOS [vs. inducible NOS (iNOS) and neuronal NOS (nNOS)] was the specific target of H 2 S regulation. H 2 S treatment (100 µmol/l) reduced Akt phosphorylation and decreased eNOS phosphorylation at Ser1177. H 2 S reduced L -Arg uptake by inhibition of a system y+ transporter and decreased the CAT-1 transcript. H 2 S treatment reduced protein expression of eNOS but not of nNOS and iNOS. Pinacidil (K ATP channel opener) exhibited the similar inhibitory effects on the L -Arg/NOS/NO pathway. Glibenclamide (K ATP channel inhibitor) partly blocked the inhibitory effect of H 2 S and pinacidil. An in vivo experiment revealed that H 2 S downregulated the vascular L -Arg/eNOS/NO pathway after intraperitoneal injection of NaHS (14 µmol/kg) in rats. Taken together, our findings suggest that H 2 S downregulates the vascular L -Arg/NOS/NO pathway in vitro and in vivo, and the K ATP channel could be involved in the regulatory mechanism of H 2 S. nitric oxide; nitric oxide synthase; L -arginine transport Address for reprint requests and other correspondence: B. Geng, Institute of Cardiovascular Research, First Hospital of Peking Univ., Beijing xishuku St. 8, 100034 (e-mail: bingeng{at}bjmu.edu.cn )