Determination of the length of the histological stages of apoptosis in normal liver and in altered hepatic foci of rats

Abstract

Apoptosis is a form of cell death involved in the regulation of cell number in various organs and tumors. Quantitative determination of cell loss through apoptosis in histological sections requires, in addition to counts of apoptotic cells, information on the duration of the histologically visible stages of apoptosis. Here we describe a method to determine the duration of apoptosis in (i) normal and (ii) putative preneoplastic tissue of the liver. (i) Female rats were treated with high doses of the hepatomitogen cyproterone acetate (CPA) to induce liver hyperplasia. After stopping CPA treatment, the hyperplasia partially regressed and excessive hepatocytes were eliminated by apoptosis. CPA was given to block the initiation of apoptosis, and thereafter the time course of elimination of apoptotic cell residues (apoptotic bodies, ABs) from the liver was studied. The mean duration of the histological stages of apoptosis was found to be approximately 3 h. (ii) Phenotypically altered cell foci in rat liver were produced by a single dose of N-nitrosomorpholine and subsequent promotion for 39 weeks with phenobarbital (PB). PB was withdrawn to stop foci growth and to stimulate apoptosis. Then rats were retreated with PB to block initiation of apoptosis in foci. The results indicate that the majority of apoptotic bodies in foci disappeared within 4 h after PB, suggesting that the stages of apoptosis are as short in foci as in normal liver. Finally a simple formula is given to calculate the cell loss rate by apoptosis. The method presented may provide data for quantitative cancer risk assessment from mathematical models of carcinogenesis.

Acute Carbon Tetrachloride Feeding Selectively Damages Large, But Not Small, Cholangiocytes From Normal Rat Liver

“…[35][36][37] Although an apoptotic rate of only 4.8% seems too low to explain our 30% reduction in overall bile duct mass, it has been shown previously that as a result of rapid turnover of apoptotic cells, a 5% apoptotic rate in the liver will result in 25% hepatocyte loss over 3 days. 48 In addition, our studies show that small cholangiocytes lining small ducts are resistant to apoptosis and that there is no loss of small ducts in our in situ morphometric analysis of intrahepatic ductal mass in CCl 4 -treated rats. Different sensitivity of various liver cell types to hepatotoxins is a well-described phenomenon.…”

Subtypes of active cell death in the granulosa of ovarian atretic follicles in the quail (Coturnix coturnix japonica)

“…However nuclear fragmentation and uptake of apoptotic bodies in heterophagosomes were not observed. As demonstrated by Bursch et al (1990b), phagocytosis and digestion of apoptotic bodies occur rapidly and it is estimated that they remain visible under light microscopy for only a few hours, so that the process can be remarkably inconspicuous. The different ratio of apoptosis versus cell necrosis found by Kovacs et al (1992) can probably be explained by the different experimental conditions.…”

Role of chemically induced cell proliferation in carcinogenesis and its use in health risk assessment.

“…Various phorbol esters, for example, reportedly block differentiation of keratinocytes (15) and can indirectly produce physical damage to cellular DNA (16,17). In the rat liver, phenobarbital prevents the death of cells in altered foci of hepatocytes (18). Thus, although the ability to induce cell proliferation appears to be necessary for tumor development, it may not be sufficient.…”