| The uptake and intracellular distribution of Na{dollar}sb2{dollar}B{dollar}sb{lcub}12{rcub}{dollar}H{dollar}sb{lcub}11{rcub}{dollar}SH, a promising boron drug for boron neutron capture therapy, were analyzed in four human cell lines (including both tumor and normal cells). The boron uptake of all four cell lines, after being exposed to 100-500 {dollar}mu{dollar}g/mL Na{dollar}sb2{dollar}B{dollar}sb{lcub}12{rcub}{dollar}H{dollar}sb{lcub}11{rcub}{dollar}SH, showed a dosage dependent increase. Boron was more concentrated in the cytoplasm than in the nucleus. There were no significant differences in boron uptake among the four cell lines. A retention experiment identified at least two different intracellular pools of boron. The cells lost {dollar}>{dollar}60% of the intracellular boron within 1 hour of being placed in B-free medium, indicating a largely low affinity binding.; The possible interference of La{dollar}sp{lcub}3+{rcub}{dollar} on intracellular calcium was investigated. Cells were incubated with LaCl{dollar}sb3{dollar} for 10 min (1 mM) or 30 min (0.1 mM), and an altered intracellular calcium distributions were observed. Compared to control cells, La{dollar}sp{lcub}3+{rcub}{dollar} treated cells released more than 0.1 mM of calcium from the Golgi complex while other cellular regions remained largely unchanged. In ouabain pre-treated cells, the loss of calcium from the Golgi complex due to La{dollar}sp{lcub}3+{rcub}{dollar} was about 4 fold higher than the ones that only treated with La{dollar}sp{lcub}3+{rcub}{dollar}. The La{dollar}sp{lcub}3+{rcub}{dollar} effect, therefore, was amplified by ouabain, possibly by Na{dollar}sp+{dollar} loading. The integrity of the Golgi complex was maintained through all the experiments. La was detected within cells and its influx was facilitated by ouabain. These results suggest that La{dollar}sp{lcub}3+{rcub}{dollar} affects cellular calcium homeostasis by entering cells and acting at least on the Golgi complex directly.; The Golgi complex was then further investigated for its role in intracellular calcium regulation. The Golgi complex was reversibly disassembled by brefeldin A. The calcium cycling in certain pools, possibly the portion sequestered in intracellular organelles, was slowed down. Also, cell response in (Ca{dollar}sp{lcub}2+{rcub}rbracksb{lcub}rm i{rcub}{dollar} to vasopressin was accentuated by brefeldin A: (Ca{dollar}sp{lcub}2+{rcub}rbracksb{lcub}rm i{rcub}{dollar} rise was suppressed by more than half. Furthermore, release of intracellular calcium by vasopressin caused a depletion in the total Golgi calcium, raising a strong possibility that the Golgi complex itself is an active calcium store, in addition to its function in protein sorting, trafficking and secretion. |
