Carcinogenesis, Vol 18, 149-158, Copyright © 1997 by Oxford University Press
YP Dragan, HA Campbell, XH Xu and HC Pitot
A modified initiation-selection procedure for neonatal male and female rat
hepatocarcinogenesis were examined utilizing the methods of quantitative
stereology. In this study, diethylnitrosamine (10 mg DEN/kg) was given a
few days after birth. At weaning, the rats were fed 0.02%
2-acetylaminofluorene (AAF) for 2 weeks with a mitotic stimulus [70%
partial hepatectomy (PH)] after 1 week on the diet. Quantitative
stereological analyses in conjunction with the use of several enzyme
markers were used to determine the number and volume of altered hepatic
foci (AHF) detected at 1 week, 3 months and 7 months after the selection
procedure. This format resulted in an equivalent number of AHF in male and
female rats. The AHF were three times larger in males than in females 1
week after discontinuation of AAF administration. Three months after the
selection procedure, the number of AHF had decreased by at least a third
and their volume percentage was the same in male and female rats. After 7
months, the number and volume fraction of detectable AHF in females were
comparable to those which had been observed at 1 week after selection. In
the male, the number but not the volume fraction were similar at 7 months
compared with 1 week after selection. Both initiation with DEN and
selection with AAF/PH contribute independently to the total population of
AHF in male and female rats. At least half of the AHF detected 7 months
after the selection protocol were due to DEN administration alone. Rats
receiving only the AAF/PH selection exhibited one third of the number of
AHF observed with the complete protocol. Administration of a non-necrogenic
dose of DEN to neonatal rats when coupled with the AAF/PH selection
procedure resulted in a significant promotion of the growth of initiated
hepatocytes at 1 week, 3 months or 7 months after the selection procedure.
These studies demonstrated that (i) the number of AHF detected after a
non-necrogenic dose of DEN during the first week of life with subsequent
AAF/PH selection after weaning decreases within the first 3 months after
the selection procedure, but can re-develop with a promotion stimulus; (ii)
the AAF/PH selection procedure itself may initiate hepatocytes in the
absence of DEN administration; (iii) the AAF/PH selection procedure is
equally effective with respect to the number of AHF observed after
phenobarbital promotion in weaning male and female rats initiated near
birth.
ARTICLES
Quantitative stereological studies of a 'selection' protocol of hepatocarcinogenesis following initiation in neonatal male and female rats
Department of Oncology, The Medical School, University of Wisconsin, Madison 53706, USA.
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