The natural history of liver regeneration in rats: description of an animal model for liver regeneration studies.
BACKGROUND
Rodent models have been used to evaluate aspects of liver regeneration. The aim of the present study was to investigate the natural history of liver regeneration in healthy rats.


METHODS
A 70% partial hepatectomy was performed in 64 rats. The animals were randomised into 8 groups and evaluated on postoperative days one to eight. Hepatocyte proliferation was evaluated by immunohistochemistry using unbiased stereological principles.


RESULTS
The mean rat body weight was 238 g (211-287). The mean weight of the resected liver was 6.3 g (5.2-7.3) and the estimated mean total liver weight was 8.9 g (7.4-10.4). Both liver weight analysis and regeneration rate showed an ascending curve, with a maximum slope on postoperative days 1-4, reaching a steady state on days 5-8. Hepatocyte proliferation (positive Ki-67 cell profiles pr. mm(2)) was high (250 cell profiles/mm(2)) on postoperative days 1-3 and tapered off on day 5.


CONCLUSION
Seventy percent partial hepatectomy in healthy rats induces a rapid regenerative response and PODs 2, 4 and 8 seems optimal for assessing hepatic growth in future studies.