Synergistic promoter effect of diethylstilbesterol & phenobarbitone in diethylnitrosamine induced hepatic neoplasia in rats.

An experimental model was designed to study the role of both diethylstilbesterol (DES) and phenobarbitone (PB) singly or in combination, in diethylnitrosamine (DEN) induced hepatic neoplasia. Experimental and control rats were injected DEN (200 mg/kg) or saline, ip. Acute morphological changes were studied at days 1, 2 and 3; and at weekly intervals for 3 wk. Four weeks after DEN pretreatment the experimental and control rats were randomized into various groups and fed DES (T1), PB (T2) or a combination of both DES and PB (T3). Five rats from each experimental group were sacrificed at 10, 20 and 30 wk. Group T3 showed gross nodules with a mean nodule score of 20.5 mm at 20 wk. Nodule score in T1, T2 and T3 at 30 wk were 7, 9 and 34.5 mm respectively. The sequential morphological lesions encountered were clear cell and acidophilic foci; acidophilic, basophilic and mixed nodules. Haemorrhage within the nodules was frequent when DES was administered either alone or in combination with PB. Oval cell proliferation and cholangiocellular lesions were produced in all experimental groups. Foci and nodules generally showed loss of glucose-6 phosphatase, adenosine triphosphatase and invariable presence of gamma-glutamyl transpeptidase and glycogen. A combination of DES and PB as promoter yielded earliest and highest nodule score. This suggests that DES and PB acted synergestically as promoters or that PB caused enzyme induction thereby enhanced the promotive effect of DES.