title: Effects of taurine and homocysteine on calcium homeostasis and hydrogen peroxide and superoxide anions in rat myocardial mitochondria.
abstract: 1. Taurine and homocysteine are metabolites of methionine. Hyperhomocysteinaemia is one of the risk factors for cardiovascular disease. Although taurine may be a cardiovascular cytoprotective substance, we hypothesized that it may antagonize the effects of homocysteine on myocardial mitochondrial function. 2. We studied the effects of taurine and homocysteine on [(45)Ca] uptake, Ca(2+)-ATPase activity and generation of hydrogen peroxide and superoxide anions in vitro in rat isolated myocardial mitochondria. 3. Results showed that the inhibition of mitochondrial [(45)Ca] uptake by homocysteine (0.1, 0.5 and 1.0 mmol/L) was concentration dependent. Taurine (5, 10 and 20 mmol/L) promoted [(45)Ca] uptake in a concentration-dependent manner, as well as concentration dependently reducing the homocysteine (0.5 mmol/L)-induced inhibition of mitochondrial [(45)Ca] uptake. 4. Homocysteine significantly inhibited mitochondrial Ca(2+)-ATPase activity, whereas taurine had a diphasic action on this activity. Taurine, at 5 and 10 mmol/L, increased Ca(2+)-ATPase activity (P < 0.01), but 20 mmol/L taurine inhibited Ca(2+)-ATPase activity (P < 0.05). Taurine attenuated the inhibitory effect of homocysteine on Ca(2+)-ATPase activity. 5. Homocysteine stimulated the generation of hydrogen peroxide and superoxide anions. Taurine had no effect on the generation of the anions, but inhibited their homocysteine-stimulated generation. 6. These results indicate that taurine and homocysteine have opposite effects in myocardial mitochondria with regard to [(45)Ca] uptake, Ca(2+)-ATPase activity and the generation of hydrogen peroxide and superoxide anions. Our results may show an important mechanism for the cardiovascular protective effects of taurine.
authors.affiliation: Institute of Cardiovascular Disease Research, The First Hospital, Beijing, People's Republic of China. changlin73@163.com
authors.forename: Lin
authors.initials: L
authors.lastname: Chang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Jianxin
authors.initials: J
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: Chao Shu
authors.initials: CS
authors.lastname: Tang
authors.forename: Yong Fen
authors.initials: YF
authors.lastname: Qi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D006710:Homocysteine / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism; D013654:Taurine / Q000494:pharmacology*
chemical_list: D006710:Homocysteine; D013481:Superoxides; D013654:Taurine; D006861:Hydrogen Peroxide; D002118:Calcium