Studies on Toxicity and Metabolism of Aflatoxin B1 in Fertile Eggs Preinjected with Edible Fats

Abstract

In order to clarify the effect of dietary fats on the acute toxicity and metabolism of aflatoxin B1 in animals, we have attempted to use fertile eggs because of technical ease in the experimental procedure.Four-day-old fertile eggs (White Leghorn) were injected into the yolk sac with 0.4ml of soybean oil, beef tallow or saline and after 2 weeks the pretreated embryos were sacrificed to prepare the hepatic soluble microsomal fraction (S-9). When aflatoxin B1 was treated with these S-9's in vitro, the amounts metabolized in 10 minutes were in the order of soybean oil-injected group (77%), saline-injected group (62%) and beef tallow-injected group (42%). The amounts of aflatoxin B1 metabolized by the S-9's were well correlated with the abilities of the S-9's to detoxify aflatoxin B1, determined from the survival rates of chick embryos injected into the air cells with S-9-treated aflatoxin B1. Estimation of the activities of the mixed function oxygenases in the S-9 and of cytoplasmic aflatoxin B1 reductase showed that the levels of p-nitroanisole demethylase, aryl hydrocarbon hydroxylase and cytoplasmic aflatoxin B1 reductase were increased in the soybean oil-injected group and decreased in the beef tallow-injected group. This suggests that soybean oil injected into the yolk sac of chick embryo might induce these hepatic enzymes and stimulate the metabolism of aflatoxin B1, resulting in detoxification in terms of acute toxicity. These results are very similar to those previously obtained with rats.The chick embryo was concluded to be a very useful tool for this type of study.