Vasorelaxation elicited by endogenous and exogenous hydrogen sulfide in mouse mesenteric arteries
H2S causes vasorelaxation however there is considerable heterogeneity in the reported pharmacological mechanism of this effect. This study examines the contribution of endogenously released H2S in the regulation of vascular tone and the mechanism of H2S-induced vasorelaxation in small resistance-like arteries. Mesenteric arteries from C57 and eNOS−/− mice were mounted in myographs to record isometric force. Vasorelaxation responses to NaHS were examined in the presence of various inhibitors of vasorelaxation pathways. Expression and activity of the H2S-producing enzyme, cystathionine-γ-lyase (CSE), were also examined. CSE was expressed in vascular smooth muscle and perivascular adipose cells from mouse mesenteric artery. The substrate for CSE, l-cysteine, caused a modest vasorelaxation (35%) in arteries from C57 mice and poor vasorelaxation (10%) in arteries from eNOS−/− mice that was sensitive to the CSE inhibitor dl-propargylglycine. The fast H2S donor, NaHS, elicited a full and biphasic vasorelaxation response in mesenteric arteries (EC50 (1) 8.7 μM, EC50 (2) 0.6 mM), which was significantly inhibited in eNOS−/− vessels (P < 0.05), unaffected by endothelial removal, or blockers at any point in the NO via soluble guanylate cyclase and cGMP (NO-sGC-cGMP) vasorelaxation pathway. Vasorelaxation to NaHS was significantly inhibited by blocking K+ channels of the KCa and KV subtypes and the Cl−/HCO3− exchanger (P < 0.05). Further experiments showed that NaHS can significantly inhibit voltage-gated Ca2+ channel function (P < 0.05). The vasorelaxant effect of H2S in small resistance-like arteries is complex, involving eNOS, K+ channels, Cl−/HCO3− exchanger, and voltage-gated Ca2+ channels. CSE is present in the smooth muscle and periadventitial adipose tissue of these resistance-like vessels and can be activated to cause modest vasorelaxation under these in vitro conditions.
KeywordsHydrogen sulfide Cystathionine-γ-lyase K+ channels Cl− channels Voltage-gated Ca2+ channels Resistance arteries
JLH was the recipient of an Australian National Health and Medical Research Council Peter Doherty Fellowship. We wish to thank Prof C Sobey and Assoc Prof B Kemp-Harper, Monash University for the eNOS−/− mouse tissue and use of laboratory facilities at Monash University. We also acknowledge the expert advice and assistance of Dr Simon Potocnik, RMIT University, for the confocal imaging and the provision of the linopirdine. We thank Prof Owen Woodman and his research group along with the technical staff at the RMIT School of Health and Biomedical Sciences for their support and assistance.
JLH conceived and designed the research, conducted experiments, analysed data and wrote the manuscript.
This study was supported by grants from the Ramaciotti Foundation and the William Buckland Foundation.
Compliance with ethical standards
This study was approved by the Monash University Department of Pharmacology Animal Ethics Committee and the RMIT University Animal Ethics Committee, Australia. This investigation conforms with the National Health and Medical Research Council (NHMRC) Australian code of practice for the care and use of animals for scientific purposes.
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