年間 4 号発行
ISSN 印刷: 2155-014X
ISSN オンライン: 2155-0158
The Role of Calcium Uniporter in Calcium Homeostasis of Extraorbital Lacrimal Gland Secretory Cells
要約
The role of mitochondrial calcium-uniporter in the control of calcium homeostasis, and correlations of calcium-uniporter with other calcium-transport systems of the rat extraorbital lacrimal gland secretory cells were studied. The experiments were performed on intact and digitonin-permeabilized cells. The interdependence of calcium-uniporter and the operation of other calcium-transporting systems were assessed on the basis of the inhibitors/agonists effects additivity, the action of which was accompanied by a decrease in Ca2+ content in the gland cells. It has been revealed that simultaneous inhibition of the calcium pump in the sarco/endoplasmic reticulum (SERCA) and mitochondrial calcium-uniporter results in a passive release of Ca2+ from different calcium stores, since the effects of the inhibitors of calcium-transport systems (thapsigargin and ruthenium red, respectively) were additive. Similarly, the effects of activation of the inositol-1, 4, 5-trisphosphate receptors (IP3Rs) and inhibition of mitochondrial calcium-uniporter were additive. In contrast, the effects of ryanodine and ruthenium red on the Ca2+ content in cells were non-additive. In addition, ryanodine at concentrations 1 − 3 µM reduced respiration rate of studied cells in a dose-dependent manner, and the effect was persisted in cells pre-incubated with ruthenium red or thapsigargin. Thus, besides the activation of ryanodine receptors (RyRs) in the endoplasmic reticulum, ryanodine inhibits Ca2+ influx in the mitochondrial matrix that was insensitive to ruthenium red.