title: L-type calcium channel blockers and EGTA enhance superoxide production in cardiac fibroblasts.
abstract: Since the recognition of the importance of calcium ions to cardiac contractility, the effects of alterations in calcium homeostasis on cardiac myocyte function have attracted immense attention. However, the possibility that changes in extracellular calcium concentration or the administration of calcium channel blockers may exert significant effects on cardiac fibroblasts has not hitherto been explored. This communication presents evidence, for the first time, that EGTA, calcium-free incubation and L-type calcium channel blockers increase endogenous superoxide production in adult rat cardiac fibroblasts. A combination of ryanodine and EGTA was found to have an even greater effect. The observations indicate that extracellular calcium levels influence endogenous superoxide production in cardiac fibroblasts and support the postulation that myocardial fibroblasts may contribute to the cardiac effects of calcium channel blockers and alterations in extracellular calcium concentration.
authors.affiliation: Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, 695 011, India. shivak@sctimst.ker.nic.in
authors.forename: K
authors.initials: K
authors.lastname: Shivakumar
authors.forename: C
authors.initials: C
authors.lastname: Kumaran
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D004110:Diltiazem / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology*; D005347:Fibroblasts / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D002121:Calcium Channel Blockers; D013481:Superoxides; D012433:Ryanodine; D004533:Egtazic Acid; D014700:Verapamil; D004110:Diltiazem; D002118:Calcium