Prolonged high intracellular free calcium concentrations induced by ATP are not immediately cytotoxic in isolated rat hepatocytes. Changes in biochemical parameters implicated in cell toxicity

Isolated rat hepatocytes were incubated with ATP to induce high intracellular free Ca2+ concentrations as determined with the Quin-2 method. Immediately after addition of ATP, the intracellular concentration of Ca2+ rose from 200 nM to more than 2.5 microM. It stayed at this value during the first 1/2 h; the rise was absolutely dependent on extracellular Ca2+. After the first 1/2 h the Ca2+ concentration decreased to 1-2 microM (5-10 times the control value). These high intracellular free Ca2+ concentrations did not lead to an immediate loss of cell viability. Only after 2 h of incubation a substantial number of cells lost viability. This was preceded by a decrease in cellular NADH (greater than 40%) and accompanied by a sharp increase in the intracellular Ca2+ concentration. Under these conditions the NADPH concentration was not affected. Cellular GSH was decreased to 30% of the initial value, but no lipid peroxidation or protein-thiol depletion was observed. Intracellular ATP, ADP and AMP were increased in the presence of extracellular ATP. Ca2+-dependent proteases seemed not to be involved in cell death. These observations are consistent with a collapse of mitochondrial functions as a final trigger of cell death.

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Allyl alcohol cytotoxicity in isolated rat hepatocytes: mechanism of cell death does not involve an early rise in cytosolic free calcium

Archives of Toxicology ◽

10.1007/s002040050132 ◽

1994 ◽

Vol 69 (1) ◽

pp. 24-29 ◽

Cited By ~ 3

Author(s):

Lora E. Rikans ◽

Yong Cai ◽

K. Roger Hornbrook

Keyword(s):

Cell Death ◽

Allyl Alcohol ◽

Rat Hepatocytes ◽

Free Calcium ◽

Cytosolic Free Calcium ◽

Isolated Rat Hepatocytes ◽

Early Rise ◽

Isolated Rat

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Peroxidase-catalyzed oxidation of 3,5-dimethyl acetaminophen causes cell death by selective protein thiol modification in isolated rat hepatocytes

Chemico-Biological Interactions ◽

10.1016/0009-2797(96)03703-9 ◽

1996 ◽

Vol 100 (3) ◽

pp. 255-265 ◽

Cited By ~ 5

Author(s):

Marianne Weis ◽

Mats Rundgren ◽

Sid Nelson ◽

Peter Moldéus

Keyword(s):

Cell Death ◽

Rat Hepatocytes ◽

Protein Thiol ◽

Isolated Rat Hepatocytes ◽

Catalyzed Oxidation ◽

Isolated Rat

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Calcium rather than cyclic AMP is an intracellular messenger of parathyroid hormone action on glycogen metabolism in isolated rat hepatocytes

Biochemical Journal ◽

10.1042/bj2580889 ◽

1989 ◽

Vol 258 (3) ◽

pp. 889-894 ◽

Cited By ~ 12

Author(s):

T Mine ◽

I Kojima ◽

E Ogata

Keyword(s):

Parathyroid Hormone ◽

Cyclic Amp ◽

Glucose Production ◽

Rat Hepatocytes ◽

Free Calcium ◽

Dependent Manner ◽

Isolated Rat Hepatocytes ◽

Glucose Output ◽

Dose Dependent ◽

Isolated Rat

The synthetic 1-34 fragment of human parathyroid hormone (1-34hPTH) stimulated glucose production in isolated rat hepatocytes. The effect of 1-34hPTH was dose-dependent and 10(10) M-1-34 hPTH elicited the maximum glucose output, which was approx. 80% of that by glucagon. Although 1-34hPTH induced a small increase in cyclic AMP production at concentrations higher than 10(-9) M, 10(-10) M-1-34hPTH induced the maximum glucose output without significant elevation of cyclic AMP. This is in contrast to the action of forskolin, which increased glucose output to the same extent as 10(-10) M-1-34hPTH by causing a 2-fold elevation of cyclic AMP. In addition to increasing cyclic AMP, 1-34hPTH caused an increase in cytoplasmic free calcium concentration ([Ca2+]c). When the effect of 1-34hPTH on [Ca2+]c was studied in aequorin-loaded cells, low concentrations of 1-34hPTH increased [Ca2+]c: the 1-34hPTH effect on [Ca2+]c was detected at as low as 10(-12) M and increased in a dose-dependent manner. 1-34hPTH increased [Ca2+]c even in the presence of 1 microM extracellular calcium, suggesting that PTH mobilizes calcium from an intracellular pool. In line with these observations, 1-34hPTH increased the production of inositol trisphosphate. These results suggest that: (1) PTH activates both cyclic AMP and calcium messenger systems and (2) PTH stimulates glycogenolysis mainly via the calcium messenger system.

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Involvement of intracellular Ca2+ and K+ in dissipation of the mitochondrial membrane potential and cell death induced by extracellular ATP in hepatocytes

Biochemical Journal ◽

10.1042/bj2880207 ◽

1992 ◽

Vol 288 (1) ◽

pp. 207-213 ◽

Cited By ~ 25

Author(s):

J P Zoeteweij ◽

B van de Water ◽

H J de Bont ◽

G J Mulder ◽

J F Nagelkerke

Keyword(s):

Cell Death ◽

Membrane Potential ◽

Mitochondrial Membrane Potential ◽

Mitochondrial Membrane ◽

Rat Hepatocytes ◽

Extracellular Atp ◽

Complete Loss ◽

Isolated Rat Hepatocytes ◽

Isolated Mitochondria ◽

Isolated Rat

Isolated rat hepatocytes were incubated with extracellular ATP to induce a prolonged increase in intracellular Ca2+ ([Ca2+]i) and a loss of viability within 2 h. By using video-intensified fluorescence microscopy, the effects of exposure to extracellular ATP on [Ca2+]i, mitochondrial membrane potential (MMP) and cell viability were determined simultaneously in individual living hepatocytes. The increase in [Ca2+]i on exposure to ATP was followed by a decreasing MMP; there were big differences between individual cells. Complete loss of the MMP occurred before cell death was observed. Omission of K+ from the incubation medium decreased the cytotoxicity of ATP; under these conditions, intracellular K+ was decreased by more than 80%. Treatment with nigericin also depleted intracellular K+ and decreased ATP-induced toxicity. Protection against loss of viability by means of a decrease in intracellular [K+] was reflected by maintenance of the MMP. These observations suggest that ATP-induced cell death may be caused by a mechanism that has been described for isolated mitochondria: after an increase in Ca2+ levels, a K+ influx into mitochondria is induced, which finally disrupts the MMP and leads to cell death.

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