An in vivo method for using 5-bromo-2'-deoxyuridine (BrdU) as a marker of chemically-induced hepatocellular proliferation in the Japanese medaka (Oryzias latipes).
Japanese medaka fish (Oryzias latipes) were used to develop an in vivo method to assess hepatocellular proliferation in a nonmammalian model. Proliferative responses were assessed in medaka at 7, 17, 24, and 94 days after a 48-hour exposure to 10 or 100 mg/L diethylnitrosamine (DEN). Subgroups of medaka were exposed to 50 or 75 mg/L of 5-bromo-2'-deoxyuridine (BrdU) in water for 72 hours, sacrificed, and then processed for immunohistochemical staining. Proliferative indices of BrdU-labeled hepatocytes were quantified and compared using both count and area measurements. There was a significant increase (p < 0.05) in hepatocellular proliferation in the 100 mg/L DEN-treated fish as compared to controls and 10 mg/L DEN-treated fish for the first 3 time points. Hepatocarcinogenicity was evaluated 26 weeks post-DEN exposure. There was a significant increase (p < 0.0001) in hepatocellular neoplasms in 100 mg/L DEN-treated fish compared to other fish. Effective BrdU-labeling of S-phase hepatocytes in medaka was achieved by adding BrdU to the aquarium water, and an increase in hepatocellular proliferation using this method was detected 7 days after exposure to a carcinogenic concentration of DEN. Additionally, the new method of area measurement indices of proliferation were as precise as count indices (R2 > or = 0.92).
Brennan
L M
LM
GEO-CENTERS, INC, Fort Detrick, Maryland 21702-5010, USA.
Boncavage-Hennessey
E M
EM
Wolfe
M J
MJ
Toussaint
M W
MW
Dennis
W E
WE
Rosencrance
A B
AB
Gardner
H S
HS
D018248:Adenoma, Liver Cell / Q000139:chemically induced / Q000473:pathology; D000818:Animals; D014408:Biomarkers, Tumor; D001973:Bromodeoxyuridine / Q000008:administration & dosage / Q000378:metabolism*; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D004052:Diethylnitrosamine / Q000633:toxicity; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D008113:Liver Neoplasms / Q000139:chemically induced / Q000473:pathology; D009990:Oryzias / Q000502:physiology*; D016196:S Phase; D013997:Time Factors
D014408:Biomarkers, Tumor; D002273:Carcinogens; D004052:Diethylnitrosamine; D001973:Bromodeoxyuridine