Unidirectional interaction between two intracellular calcium stores in rat phaeochromocytoma (PC12) cells.
1. A clone of the rat phaeochromocytoma cell line (PC12) was treated with nerve growth factor (NGF) for 4-6 days and used to study caffeine- and bradykinin-induced Ca2+ release from intracellular Ca2+ stores. The caffeine-sensitive store can be depleted by Ca(2+)-induced Ca2+ release (CICR), while the bradykinin-induced release is mediated by inositol 1,4,5-trisphosphate (IP3). The effect of Ca2+ release from these Ca2+ stores on cytosolic free Ca2+ ([Ca2+]i) was measured by means of fura-2 single cell microfluorimetry. 2. Caffeine application caused no or only a small Ca2+ release in untreated cells in normal culture medium. The caffeine-sensitive pool could be filled by Ca2+ entry into cells through either voltage-activated Ca2+ channels or ligand-gated cation channels. 3. Bradykinin application produced substantial Ca2+ release in untreated cells in normal culture medium. The response was enhanced after K(+)-depolarization of the cells. The bradykinin-induced release of Ca2+ also caused depletion of the caffeine-sensitive pool by CICR. However, Ca2+ released from the IP3-sensitive store was not sequestered into the caffeine-sensitive Ca2+ store. 4. The caffeine-induced rise in [Ca2+]i was blocked by ryanodine in a use-dependent manner. In addition, a substantial use-dependent ryanodine block resulted from the bradykinin-induced rise of [Ca2+]i and subsequent CICR. By contrast, the K(+)-induced rise of [Ca2+]i caused only a marginal use-dependent ryanodine inhibition of Ca2+ release. 5. Our results suggest an enhancement of the IP3-induced [Ca2+]i rise in the cytoplasm by CICR from the caffeine-sensitive pool. 6. A mathematical model adequately simulates our experimental data.
Reber
B F
BF
Department of Pharmacology, University of Bern, Switzerland.
Stucki
J W
JW
Reuter
H
H
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers; D003198:Computer Simulation; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008954:Models, Biological; D009124:Muscle Proteins / Q000037:antagonists & inhibitors; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016716:PC12 Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel; D015398:Signal Transduction
D002121:Calcium Channel Blockers; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D001920:Bradykinin; D002118:Calcium