Ca2+ homeostasis and cytotoxicity in isolated hepatocytes: studies with extracellular adenosine 5'-triphosphate.
The incubation of isolated rat hepatocytes with extracellular adenosine 5'-triphosphate (ATP) resulted in an inhibition of Ca2+ efflux. The ATP-induced Ca2+ accumulation as determined by the increase in phosphorylase a activity and the Ca2+-sensitive fluorescent indicator (2-[(2-bis-[carboxymethyl]-amino-5-methylphenoxy)-methyl]-6-methoxy-8- bis-[carboxymethyl]aminoquinoline-tetrakis-[acetoxymethyl]ester) (Quin 2-AM) was associated with both the hydrolysis of ATP and the phosphorylation of a 110 kDa protein. No significant alteration in the intracellular ATP level was observed. The appearance of surface blebs and cytotoxicity followed the rise in cytosolic Ca2+, suggesting that the increased free Ca2+ may be responsible for the loss of viability. When a calmodulin inhibitor, 1-[bis(4-chlorophenyl)methyl]-3-[ 2-(2,4-dichlorophenyl)-2-[(2,4-dichlorophenyl)methoxy] ethyl]-1H- imidazolium chloride (calmidazolium), was included in the medium prior to ATP addition, bleb formation was reduced and the loss of viability was completely prevented, indicating that a Ca2+-calmodulin process may be involved in the initiation of cytotoxicity.
Mirabelli
F
F
Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
Bellomo
G
G
Nicotera
P
P
Moore
M
M
Orrenius
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002147:Calmodulin / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010762:Phosphorylase a / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains
D000634:Aminoquinolines; D002147:Calmodulin; D007093:Imidazoles; C031938:calmidazolium; C035738:Quin2-acetoxymethyl ester; D000255:Adenosine Triphosphate; D010762:Phosphorylase a; D002118:Calcium