Ginkgo biloba (EGb) has been proposed as a promising candidate
for cancer chemoprevention and has shown protective e
ffects on the liver against chemically induced oxidative injury and
fibrosis. The potential bene
ficial e
ffects o
f EGb were investigated in two rat liver carcinogenesis bioassays induced by diethylnitrosamine (DEN). In a short-term study
for anti-initiating screening, male Wistar rats were
fed a basal diet or supplemented diet with 500 or 1000 ppm EGb and initiated 14 days later with a single dose o
f DEN (100 mg/kg i.p.). The respective groups were killed 24 h or 2 weeks a
fter DEN-initiation. Liver samples were collected
for the analysis o
f proli
ferating cell nuclear antigen (PCNA), trans
forming growth
factor alpha (TGF-
f"" alt=""greek small letter alpha"" title=""greek small letter alpha"" border=""0"">), p53, apoptosis and induction o
f single hepatocytes and mini
foci positive
for the enzyme glutathione
S-trans
ferase P-
form (GST-P). In a medium-term study
for anti-promoting screening, the animals received a single dose o
f DEN (200 mg/kg i.p.) and, 2 weeks later, were
fed a basal diet or supplemented diet with 500 or 1000 ppm EGb
for 6 weeks. All animals underwent 70 % partial hepatectomy (PH) at week 3 and killed at week 8. Liver samples were colleted to analyze development o
f preneoplastic
foci o
f altered hepatocytes (FAH) expressing GST-P. In the short-term study, pretreatment o
f rats with 1000 ppm EGb signi
ficantly reduced the rates o
f cell proli
feration, apoptosis and p53, TGF-
f"" alt=""greek small letter alpha"" title=""greek small letter alpha"" border=""0""> immunoreactivity and the number o
f GST-P-positive hepatocytes. In the medium-term study, EGb treatment during the post-initiation stage
failed to reduce the development o
f DEN-induced GST-P-positive
foci. Thus, EGb presented inhibitory actions during initiation but not promotion o
f rat liver carcinogenesis induced by DEN.