title: Caffeine-induced Ca2+ oscillations in type I horizontal cells of the carp retina and the contribution of the store-operated Ca2+ entry pathway.
abstract: The mechanisms of release, depletion, and refilling of endoplasmic reticulum (ER) Ca2+ were investigated in type I horizontal cells of the carp retina using a fluo-3-based Ca2+ imaging technique. Exogenous application of caffeine, a ryanodine receptor agonist, induced oscillatory intracellular free Ca2+ concentration ([Ca2+]i) responses in a duration- and concentration-dependent manner. In Ca2+-free Ringer's solution, [Ca2+]i transients could also be induced by a brief caffeine application, whereas subsequent caffeine application induced no [Ca2+]i increase, which implied that extracellular Ca2+ was required for ER refilling, confirming the necessity of a Ca2+ influx pathway for ER refilling. Depletion of ER Ca2+ by thapsigargin triggered a Ca2+ influx which could be blocked by the store-operated channel inhibitor 2-APB, which proved the existence of the store-operated Ca2+ entry pathway. Taken together, these results suggested that after being depleted by caffeine, the ER was replenished by Ca2+ influx via store-operated channels. These results reveal the fine modulation of ER Ca2+ signaling, and the activation of the store-operated Ca2+ entry pathway guarantees the replenishment of the ER so that the cell can be ready for response to the subsequent stimulus.
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Lv
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Hai-Qing
authors.initials: HQ
authors.lastname: Gong
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Pei-Ji
authors.initials: PJ
authors.lastname: Liang
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002347:Carps / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000378:metabolism
chemical_list: D002110:Caffeine; D002118:Calcium