Minimal dose and time protection by lindane (γ‐isomer of 1,2,3,4,5,6 hexachlorocyclohexane) against liver tumors induced by aflatoxin b 1

This study was carried out in order to investigate the minimal exposure to lindane (LD, 99.72% gamma isomer of 1,2,3,4,5,6 hexachlorocyclohexane), a chlorinated hydrocarbon insecticide, required to protect against liver tumor induced by aflatoxin B 1 (AFB 1 ). Materials fed to Buffalo strain rats were as follows: LD 100 ppm; AFB 1 I ppm, LD 100 ppm plus AFB 1 1 ppm; and control basal diet. The experimental animals were clinically observed and then serially killed at 1, 3, 5, 10, 15 and 82 weeks. Concurrent administration of LD with AFB 1 to rats for more than 3 weeks totally inhibited the incidence of AFB 1 ‐induced hepatocellular carcinomas by week 82. Only 1 of 20 rats (5%) fed the same regimen for 1 week developed liver tumors. Animals given 1 ppm AFB 1 singly for 15 weeks had a high liver tumor incidence (31.5%). No animals developed liver tumors in LD‐treated and control groups. LD may inhibit AFB 1 ‐induced liver tumors by stimulating hepatic metabolism and excretion of AFB 1 so that less carcinogen is available to liver tissue.