DECLINE IN PLASMA-MEMBRANE CA2-ATPASE ACTIVITY AND INCREASE IN CYTOSOLIC-FREE CA2+ CONCENTRATION OF ENDOTOXIN-INJECTED MICE LIVERS( )

The present study describes the activity of Ca2+-ATPase in liver plasm a membrane and cytosolic-free Ca2+ concentration ([Ca2+]i) in an indiv idual vital cell in mouse liver 18 h after endotoxin administration. C a2+-ATPase activity in liver plasma membrane in the poisoned mice was markedly decreased to 28% of that in the control. The membrane protein damage in liver was found mostly in the molecular weight (M.W.) regio ns near 60000-150000 in endotoxemic mice, and was markedly injured nea r 140000 (M. W. of Ca2+-ATPase in liver plasma membrane). The level of [Ca2+]i in liver cells in endotoxin-poisoned mice was greater at 18 h postintoxication than that of the control. These findings suggest the possibility that the depression of Ca2+-ATPase activity in liver plas ma membrane in mice may contribute to membrane damage caused by the en dotoxin, and that the increase of [Ca2+]i in liver cytoplasm may parti ally explain various endotoxin-induced metabolic disorders.