Response of human hepatocyte lysosomes to postmortem anoxia

We studied the ultrastructure and degradative activity of lysosomes in human livers after somatic death due to cerebral necrosis secondary to shock and/or head trauma. The livers were obtained at autopsy after varying postmortem intervals. Liver ultrastructure was studied in intact liver, in hepatocyte suspension obtained by collagenase perfusion of the liver, and in cultured hepatocytes. Lysosomal protein degradation was measured in a case 24 hours after hepatocyte isolation. By standard ultrastructural criteria, all the livers demonstrated typical reversible manifestations of cell injury. Most hepatocytes demonstrated varying degrees of irreversible cell injury. The ultrastructural alterations were less severe in the isolated hepatocytes in suspensions, and further improvement in morphologic appearance occurred in the cultured monolayers. The most striking alteration in the liver lysosomes was the increase in the numbers of lipofuscin granules (a type of residual body) compared with control liver. The hepatocyte lysosomes constituted an average 3.1% of cytoplasmic volume. There was no correlation between the volume density of lysosomes and either the duration of postmortem anoxia, clinical course, or patient's age. There was no increase in the number of autophagic vacuoles or of secondary lysosomes in postmortem liver. Autophagic vacuoles were more frequently seen in isolated and cultured hepatocytes. Cultured hepatocytes isolated within one hour of clinical death and tested 24 hours later degraded cell proteins at a rate of 1.7% per hour. Protein degradation was stimulated by a physiologic signal (Dibutyryl cAMP, 1 mmol/L) and was inhibited by microtubule poison (vinblastine). We conclude that (1) viable hepatocytes can be isolated even after prolonged postmortem intervals (range, 30 minutes to seven hours), (2) trauma and shock cause an expansion of hepatocyte lysosomes due to accumulation of lipofuscin, and (3) autophagy is blocked by postmortem anoxia and resumes in the recovery phase from anoxic injury in hepatocyte suspensions and in culture.