COMPARISON OF THE PATTERN OF DIST RI BUTION OF AFLATOXIN B 1 METABOLITES IN ADULT AND NEWBORN RATS

Recently we have reported that newborn rats are deficient in the key enzymes involved in the biotransformation of aflatoxin Bl (AFBl), a known hepatocarcinogen. Based on these data, in vivo experiments were carried out in order to investigate the bioavailability of this carcinogen in newborn rat tissues. Administration of a single dose (i. p.) of [3HlAFB 1 to groups of adult and neonatal rats resulted in the differential distribution of AFB 1 metabolites in these animals. Uptake of aflatoxins by neonatal rats was about 50% of that in adults at all time intervals. In newborn liver, the level of aflatoxin reached its maximum 6 h after injection, and gradually decreased during the following 12 aod 24 h. In adult liver the uptake was highest 2 h after AFB 1 administration. A decrease of radioactivity in liver relative to time was associated with a surge in aflatoxin levels in the sera of both age groups. Excretion of AFB 1 metabolites was comparatively faster from newborn than from adult kidneys. Much lower radioactivity was measured in tissues such as stomach, intestine and lungs compared to liver. These observations indicate that the neonatal rat liver is less efficient in the bioactivation of AFBl, as a result of which free AFB 1 (nonmetabolized) may remain for a longer period of time in the organs of immature rats.