CALCIUM-INDUCED CONVERSION OF ADENINE-NUCLEOTIDES TO INOSINE MONOPHOSPHATE IN HUMAN RED-CELLS
CALCIUM-INDUCED CONVERSION OF ADENINE-NUCLEOTIDES TO INOSINE MONOPHOSPHATE IN HUMAN RED-CELLS
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DOI：
10.1113/jphysiol.1988.sp017431
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发表时间：
1988-12-01
影响因子：
5.5
通讯作者：
LEW, VL
中科院分区：
文献类型：
--
作者：
ALMARAZ, L;GARCIASANCHO, J;LEW, VL
1.当肌苷喂养的人红细胞通过暴露于离子载体A23187而透化钙时，随着钙内流的增加，越来越大比例的细胞群变得不可逆地消耗ATP（Brown和Lew，1983; Garcia-Sancho和Lew，1988 b）。当钙内流超过30 mmol/（l细胞. h）时，所有细胞都变得ATP耗尽，钙平衡（E细胞）（Garcia-Sancho和Lew，1988 b）。当钙内流较低时，E细胞与能够维持正常ATP和低钙含量的细胞（B细胞）共存于强泵漏平衡中。本文报道的实验研究了为什么钙诱导的E细胞ATP耗竭是不可逆的。2.肌苷一磷酸（IMP）含量的细胞后30分钟的钙透性增加的幅度的钙负荷，大致成反比的ATP的下降。钙诱导的IMP增加仅限于SCN处理后变得耐药的细胞部分（H细胞），其中包含E细胞。3.在具有不同[Ca 2-]o（0-0.5 mM）的无基质培养基中进行钙透化（[A23187]c = 100 μ mol/l细胞）后测量细胞核苷酸。在所有[Ca ~（2+）]o浓度下，钙离子进入引起ATP快速下降，AMP和IMP积累，ADP下降延迟。初始IMP形成随[Ca 2 +]o沿着S形饱和样曲线增加，而AMP积累和ATP下降在[Ca 2 +]o = 20 μ M时最大，并在较高[Ca 2 +]o时下降。在所有[Ca ~（2+）]o值下，IMP形成率与细胞ATP呈正相关，与细胞AMP呈负相关。4.钙可使红细胞裂解物的AMP脱氨酶活性可逆性增加10倍以上。在约50 μ M的Ca 2+浓度下观察到半最大刺激。5.这些结果表明，不可逆的钙诱导的ATP耗竭的结果从不可逆的捕获腺嘌呤核苷酸作为IMP，并帮助解释E细胞形成的机制。
1. When inosine-fed human red cells are permeabilized to calcium by exposure to the ionophore A23187, progressively larger proportions of the cell population become irreversibly depleted of ATP as calcium influx is increased (Brown and Lew, 1983; Garcia-Sancho and Lew, 1988b). When calcium influx is over 30 mmol/(l cells.h), all cells become ATP depleted and calcium equilibrated (E cells) (Garcia-Sancho and Lew, 1988b). When calcium influx is lower, E cells co-exist with cells able to maintain normal ATP and low calcium contents in vigorous pump-leak balance (B cells). The experiments reported here investigate why calcium-induced ATP depletion of E cells is irreversible. 2. The inosine monophosphate (IMP) content of cells after 30 min of calcium permeabilization increased with the magnitude of the calcium load, roughly in inverse proportion to the fall in ATP. The calcium-induced increase in IMP was confined to the fraction of cells which became osmotically resistant after SCN-treatment (H cells), and which contained the E cells. 3. Cell nucleotides were measured after calcium permeabilization ([A23187]c = 100 .mu.mol/l cells) in substrate-free media with different [Ca2-]o (0-0.5 mM). Calcium entry caused rapid ATP fall, AMP and IMP accumulation, and delayed ADP fall at all [Ca2+]o concentrations. Initial IMP formation increased with [Ca2+]o along a sigmoid saturation-like curve whereas AMP accumulation and ATP fall were maximal at [Ca2+]o = 20 .mu.M and declined at the higher [Ca2+]o. The rate of IMP formation correlated positively with cell ATP and negatively with cell AMP at all [Ca2+]o values. 4. The AMP deaminase activity of red cell lysates was reversibly increased over tenfold by calcium. Half-maximal stimulation was observed at a Ca2+ concentration of about 50 .mu.M. 5. These results suggest that the irreversibility of calcium-induced ATP depletion results from irreversible trapping of the adenine nucleotide as IMP, and help explain the mechanism of E cell formation.