Enhancing effect of co-administration of polychlorinated biphenyls and diethylnitrosamine on enzyme-altered islands induced by diethylnitrosamine in rat liver

The effect of co-adminstration of diethytnitrosamine (DEN) andClophen A 50, a commercial mixture of polychlorinated biphenyls(PCB), on pre-neoplastk enzyme-altered islands in livers offemale Sprague-Dawley rats was studied. The islands were identifiedby the loss of adenosine-5'triphos-phatase (ATPase), emergenceof gamma-glutamyltranspep-tidase (GGTase) and glycogen storageafter fasting. DEN was given p.o. (0.4 or 4 mg/kg body wt respectively)twice a week for 11 consecutive weeks. Clophen A 50 (1 or 5mg/kg body wt respectively) was given alternatively three timesa week for 11 weeks. Four groups of rats each received eitherDEN or PCBs in the respective doses. Control animals were treatedwith the vehicle or remained untreated. All animals were killedat week 12. In rats treated with 4 mg DEN/kg body wt 80 ATPase-defidentislands/cm2 were observed. Additional treatment with ClophenA 50 enhanced the island number 3-fold. Treatment with 0.4mg/kg body wt DEN induced 17 islands/cm². Additional applicationof Clophen A 50 enhanced the island number 3-fold. The totalisland area was enhanced to the same extent in both groups.The island incidence in PCB-treated rats and controls was belowI/cm² with all markers tested. The results indicate that PCBsmay exhibit a co-carcinogenic activity.