Intracellular calcium concentration impairment in hepatocytes from thioacetamide-treated rats. Implications for the activity of Ca(2+)-dependent enzymes.
RESULTS
Thioacetamide induced a severe perivenous necrosis followed by a hepatocellular regenerative response, when administered in a single dose of 6.6 mmol/kg to rats. As (Ca2+)i plays an important role in both toxic cell killing and cell proliferation, the disturbances in the basal cytosolic calcium as well as the levels of Ca2+ sequestered in the endoplasmic reticulum were determined in hepatocytes isolated at 0, 12, 24, 48 and 72 h after thioacetamide administration. The basal Ca2+ increased progressively, reaching a maximum at 24 h of the intoxication (205%, p < 0.001), while the microsomal sequestered Ca2+ decreased at 24 h to 16% (p < 0.001) when compared with untreated controls. Changes in the activity of glycogen phosphorylase alpha paralleled those of basal free calcium and showed the maximum value also at 24 h (291%; p < 0.001). Moreover, there was a close association in time between the basal concentration of Ca2+ and the inhibition of microsomal Ca(2+)-dependent ATPase activity.


CONCLUSIONS
The significant decrease in the levels of GSH and protein thiols indicates that oxidative stress is involved in thioacetamide-induced cell injury, but these decreases did not precede changes in cytosolic Ca2+ level. In the sequence of events leading to hepatic cell injury and regeneration, thioacetamide mobilized hepatic (Ca2+)i via inhibition of microsomal Ca(2+)-ATPase which may have activated Ca(2+)-dependent mechanisms involved both in cell death and in acute mitogen response.
Díez-Fernández
C
C
Instituto de Bioquímica (CSIC-UCM), Falcultad de Farmacia, Universidad Complutense, Madrid, Spain.
Sanz
N
N
Cascales
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives / Q000378:metabolism; D019803:Glutathione Disulfide; D007425:Intracellular Membranes / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008115:Liver Regeneration / Q000187:drug effects; D008297:Male; D009994:Osmolar Concentration; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013853:Thioacetamide / Q000494:pharmacology*
D013853:Thioacetamide; D006005:Phosphorylases; D000252:Calcium-Transporting ATPases; D005978:Glutathione; D002118:Calcium; D019803:Glutathione Disulfide