The role of L-cysteine/H2S pathway in CaSRs-mediated relaxations in mouse bladder tissue

The activation of Calcium-Sensing Receptors (CaSRs) reduces detrusor activity in bladder tissues. Also, hydrogen sulfide (H2S) produces in bladder tissue and regulates the bladder smooth muscles tone. However, there is no evidence of the interaction between CaSRs and H2S in bladder tissue. The aim of this study is to investigate the possible contribution of L-cysteine/H2S pathway in CaSRs-mediated relaxation responses in isolated mouse bladder tissue. CaCl2 (1, 2, 3, 5, 10 mM) was applied to isolated mouse bladder tissues pre-contracted with carbachol (1 microM). CaCl2-induced relaxations were performed in the presence of PAG (10 mM), AOAA (1 mM), and Calhex-231 (5 microM), cystathionine-gamma-lyase (CSE), cystathionine-beta-synthase (CBS) and CaSR inhibitor, respectively. L-cysteine (1 microM-10 mM), an H2S substrate, was used to induced a concentration-dependent relaxant response in isolated bladder tissues pre-contracted with carbachol. L-cysteine induced relaxations were performed in the presence of PAG (CSE inhibitor, 10 mM), AOAA (CBS inhibitor, 1 mM) and Calhex-231 (CaSR inhibitor, 5 microM). CaCl2-induced relaxations were decreased by PAG and AOAA. Also, Calhex-231 decreased the CaCl2-induced relaxant responses. L-cysteine-induced relaxant responses were reduced in the presence of PAG (10 mM) and AOAA (1 mM). Calhex-231 (5 microM) caused a significant decrease in L-cysteine-induced relaxations. Also, Calhex-231 reduced the increase in H2S production in the presence of L-cysteine. In addition, CaCl2 increased basal H2S generation, and PAG (10 mM), AOAA (1 mM) and Calhex-231 (5 microM) reduced the increase in H2S production stimulated with CaCl2. In conclusion, CSE and CBS-derived endogenous H2S formation may, at least in part, contribute to CaSR-mediated relaxation responses, and CaSRs involve in endogenous H2S relaxation responses in isolated mouse bladder tissue. Key words Bladder o CaSRs " Calhex-231 " Hydrogen sulfide " L-cysteine " Mouse.