Sequence and Rate of Postmortem Autolysis in Guinea Pig Liver

Abstract

SUMMARY The sequence and the rate of postmortem changes in liver of intact guinea pig (Cavia porcellus) cadavers were determined. Guinea pigs were electrocuted, and unopened cadavers were maintained at 20 C, 50% relative humidity, for 0 to 48 hours. Liver was fixed in 10% buffered neutral formalin (bnf) and in Zenker's fluid. Hepatic sections fixed 1.5 hours after death had the best presentation of lobules. There was negligible postmortem autolysis, and the sinusoids were distended with blood. Sections prepared prior to 1.5 hours after death had collapsed sinusoids because unclotted blood flowed from the cut surface. Hepatocytic cytoplasmic basophilia started to disappear centrilobularly at 0.75 hour and had been completely lost by 3 hours. Hepatocyte nuclei disappeared almost entirely by karyolysis. Nuclear fading accompanied by margination of the nuclear chromatin was present by 9 hours. After 48 hours, approximately 25% of the hepatocyte nuclei had lysed. Pyknotic hepatocyte nuclei were rarely observed, but pyknosis of Kupffer's cells began as early as 1.5 hours, with the majority being markedly pyknotic after 9 hours. Individualization of the hepatocytes and an obvious space of Disse were first seen at 6 hours. The space of Mall was rarely seen. Separation of bile-duct epithelium from basement membranes began at 18 hours and was present in most bile ducts by 24 hours. Zenker-fixed tissues differed significantly from 10% bnf fixed tissues only in their lack of contrast, retention of tissue basophilia up to 9 hours, and delayed onset of hepatocyte individualization which was first seen at 9 hours. Even after 24 hours, hepatic sections were still useful for diagnostic purposes and some lesions such as fibrosis would be readily recognizable after 48 hours at 20 C.