頁籤選單縮合
題名 | Nω-Nitro-L-Arginine Decreases Resting Cytosolic [Ca[fec7]] and Enhances Heat Stress-Induced Increase in Cytosolic [Ca[fec7]] in Human Colon Carcinoma T84 Cells |
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作者 | Kiang,Juliann G.; McClain,David E.; | 書刊名 | 中國生理學雜誌 |
卷期 | 42:3 1999.09[民88.09] |
頁次 | 頁153-159 |
分類號 | 361.8 |
關鍵詞 | Na狇/Ca[fec7]exchanger; Ca[fec7]; No synthase; Heat stress; Colon; |
語文 | 英文(English) |
英文摘要 | Nw-nitro-L-arginine (LNNA) inhibits the synthesis of heat shock proteins in animals and cultured cells exposed to heat stress. Heat shock protein synthesis is known to be Ca U -dependent. In this study, we have characterized the effect of LNNA on [Ca U ] | before and after heat stress in human colon carcinoma T84 cells. In untreated cells incubated in the presence of external Ca U, the resting [Ca U ] | was 201 ± 3 nM. If these cells were exposed to 45 for 10 min, [Ca U ] | increased by 50 ± 2%. Preincubation with LNNA (100 ? M) without subsequent heating led to a decrease in [Ca U ] | in a LNNA concentration-dependent manner. Preincubation with LNNA followed by heating increased [Ca U ] | to levels 88 ± 5% greater than cells heated without LNNA pretreatment. Incubating cells in medium without external Ca U (no heating, no LNNA treatment) lowered resting [Ca U ] | to 115 ± 2 nM and greatly reduced the increase in [Ca U ] | observed if cells were heated in the presence of Ca U, indicating that external Ca U plays an important role in the maintenance of [Ca U ] | in T84 cells. With external Ca U absent, LNNA pretreatment further reduced [Ca U ] | in unheated cells, and heating failed to enhance [Ca U ] |. We determined (with external Ca present) that the heat-stress induced increase in [Ca U ] | in T84 cells was blocked by dichlorobenzamil, a Na ? /VCa U exchanger inhibitor, suggesting that the exchanger mediates Ca U entry. The median inhibitory concentration (IC 1) in cells not treated with LNNA was 0.970 ± 0.028 ? M. With LNNA pretreatment, the IC 1 was 5.099 ± 0.107 ? M. Heat stress of T84 cells did not affect the binding affinity of the Na ? /Ca U exchanger for external Ca U, but it increased the maximal velocity of the exchanger. In unheated cells, preincubation with LNNA decreased the binding affinity of the exchanger for Ca U, but after heat treatment, both the binding affinity and maximal velocity of the exchanger increased. Our data are consistent with the idea that LNNA affects the activity of the Na ? /Ca U exchanger. We also determined there are intracellular Ca U pools in T84 cells sensitive to thapsigargin, monensin, and ionomycin. Treatment with TMB-8, a blocker of Ca U sequestration and mobilization, or ionomycin inhibited the LNNA-induced decrease in [Ca U ] | observed in the absence of external Ca U, suggesting that LNNA promotes Ca U sequestration. esting that LNNA promotes Ca�� sequestration. |
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