The anti-anginal drug fendiline elevates cytosolic Ca(2+) in rabbit corneal epithelial cells.
The effect of the anti-anginal drug fendiline on intracellular free Ca(2+) levels ([Ca(2+)](i)) in a rabbit corneal epithelial cell line (SIRC) was explored using fura-2 as a fluorescent Ca(2+) indicator. At a concentration above 1 microM, fendiline increased [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 7 microM. The [Ca(2+)](i) response consisted of an immediate rise and an elevated phase. Extracellular Ca(2+) removal decreased half of the [Ca(2+)](i )signal. Fendiline induced quench of fura-2 fluorescence by Mn(2+) (50 microM), suggesting the presence of Ca(2+) influx across the plasma membrane. This Ca(2+) influx was abolished by La(3+) (50 microM), but was insensitive to dihydropyridines, verapamil and diltiazem. Fendiline (10 microM)-induced store Ca(2+) release was largely reduced by pretreatment with thapsigargin (1 microM) (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+). Conversely, pretreatment with 10 microM fendiline abolished thapsigargin-induced Ca(2+) release. Fendiline (10 microM)-induced Ca(2+) release was not altered by inhibiting phospholipase C with 2 microM 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Cumulatively, this study shows that fendiline induced concentration-dependent [Ca(2+)](i )increases in corneal epithelial cells by releasing the endoplasmic reticulum Ca(2+) in a phospholipase C-independent manner, and by causing Ca(2+) influx.
Lin
Muh Chiou
MC
Department of Ophthalmology, Kaohsiung Veterans General Hospital, 813, Kaohsiung, Taiwan.
Jan
Chung Ren
CR
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects* / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D005275:Fendiline / Q000494:pharmacology*; D011817:Rabbits; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014665:Vasodilator Agents / Q000494:pharmacology*
D002147:Calmodulin; D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D010738:Type C Phospholipases; D005275:Fendiline; D002118:Calcium