Susceptibility to the hepatocarcinogen Aflatoxin B1 (AFB1) varies among species and with age. Mice are refractory to carcinogenic and toxic effects of AFB1; however, B6C3F1 mice show transient sensitivity if dosed shortly after birth. We compared age-related differences in gene expression and transcriptional responses to AFB1 in livers of newborn (4-day-old) and adult mice. Keywords: Transcriptional response to a carcinogen
Overall design
Experiments were carried out under the protocol approved by MIT Animal Care Committee. Pregnant C57BL/6J female mice, mated to C3H/HeJ males, and adult (at least 60 day-old) B6C3F1/J hybrid F1 male mice (C57BL/6J female x C3H/HeJ male) were obtained from Jackson Labs. They were housed in plastic cages (one per cage) under controlled environmental conditions and 12 h light/dark cycle. Food and water were supplied ad libitum. After female mice gave birth, the male B6C3F1 pups were dosed at 4 days by a single i.p. injection of AFB1 (6 mg/kg body weight) in DMSO (10 ml/kg body weight) or the same volume of just DMSO. The treatments were always performed at the same time of the day and the pups were returned to their mothers until they were sacrificed 4 or 24 h after treatment. Adult B6C3F1 males were treated with the same doses and volumes of AFB1 or DMSO after an acclimation period of at least two weeks and sacrificed 4 or 24 hours after treatment. We noticed that injection of a volume of 10 ml/kg (whether AFB1 or vehicle alone) is tolerated poorly by adult animals and thus another group of adult animals was added which was treated with the same (6 mg/kg) dose of AFB in lower (5 ml/kg) volume. Corresponding vehicle control animals (5ml/kg DMSO) were also used. In addition, untreated controls were used and sacrificed together with the treated animals. Three independant bilogical replicates were used for each experimental point. Total RNA was isolated from livers and processed according to standard Affymetrix protocol.
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