Free cytoplasmic Ca2+ concentration oscillations in thapsigargin-treated parotid acinar cells are caffeine- and ryanodine-sensitive.
The microsomal Ca-ATPase inhibitor thapsigargin induces in rat salivary acinar cells [Ca2+]i oscillations which, though similar to those activated by agonists, are independent of inositol phosphates or inositol 1,4,5-trisphosphate (IP3)-sensitive intracellular Ca2+ stores (Foskett, J. K., Roifman, C., and Wong, D. (1991) J. Biol. Chem. 266, 2778-2782). To examine whether the oscillation mechanism resides in another, thapsigargin- and IP3-insensitive intracellular store, we examined the effects of caffeine and ryanodine, known modulators of Ca2+ release from sarcoplasmic reticulum in excitable cells. Oscillations were induced by caffeine (1-20 mM) in nonoscillating thapsigargin-treated acinar cells, which required the continued presence of caffeine, whereas caffeine was without effect or reduced oscillation amplitude in oscillating cells. Ryanodine (10-50 microM) inhibited oscillations in most of the cells. These results suggest that Ca2+ oscillations in parotid acinar cells are driven by periodic Ca2+ release from an IP3-insensitive Ca2+ store with properties similar to sarcoplasmic reticulum of excitable cells.
Foskett
J K
JK
Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada.
Wong
D
D
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008297:Male; D010306:Parotid Gland / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012433:Ryanodine / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
D013729:Terpenes; D012433:Ryanodine; D002110:Caffeine; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium