Cell proliferation in the liver: A malpractice not to measure the zonal distribution? Comparison of the lobule-dependent zonal measurement method with the common method of randomly distribute measurement fields

• Published in: Toxicology methods 2000-04, Vol.10 (2), p.81-97
• Main Author: Bahnemann, R
• Format: Article
• Language: English
• Subjects: butylated hydroxytoluene
• ISSN: 1051-7235
• DOI: 10.1080/10517230050083339

Measurement of cell proliferation in the liver is usually performedby evaluating randomly distributed measurement fields (RADI). This ignores the fact that liver lobules consist of different cell populations and increases the risk of overlooking biologically relevant effects. Therefore, the lobule-dependent zonal measurement (LZM) method was developed to guarantee the independent evaluation of the hepatic zones in lobules of comparable size. To prove this concept, routinely performed studies on cell proliferation were examined in parallel for both methods. Phenobarbital (PB), butylated hydroxytoluene (BHT), and four agrochemicals (AChI-IV)were given for 1, 6, and 13 weeks to 8-12-week-old Wistarrats via the diet. According to the high dose and dosing regimen employed in the life span bioassay, the animals received the test substance at a maximum tolerated dose. Hepatocellular proliferation studies were performed by subcutaneously implanting osmotic minipumps to continuously deliver 5-bromo-2-deoxiuridine for 7 d. Inanadditional study, phenacetin(PH) was fed for 4 weeks to gain information about the optimal Bromodeoxyuridine (BrdU) application time (2 h, d, and 7 d) for liver. For BHT and AChII, both methods described nearly the same proliferation pattern. In the cases of AChIII and IV, the RADI evaluation evokes the impression of a transient increase of proliferation after 1 week of application. In contrast, the zonal-based measurement additionally showed a strong sustained effect in zone 3 (perivenous) even after 13 weeks, an effect which can be clearly correlated to the development of tumors. For PB, ACh I, and PH, a significantly higher number of misleading outliers was observed by using RADI, compared to LZM. The data show that the risk of overlooking effects increases with a decrease in positively labeled cells. The lobule-dependent measurement strategy lowers the sensitivity to outliers and leads, by providing additional information on target zones, to a better correlation with tumor data. Both aspects imply a strong impact on retrospective and predictive evaluations of cell proliferationin the liver.