Purpose: To study the effects of drinking water contaminated with microcystins(MC) on cell prolife \{ration\} and apoptosis during the course of hepatocarcinogenesis,and to probe the mechanism of promoting hepatocarcinogenesis of microcystic toxins. Methods: 50 healthy Wistar rats were randomly divided into 4 groups: group A (normal control); group B (treated with DEN only); group C (treated with DEN and MC contaminated water); group D (treated with DEN and microcystins i.p ). The PCNA, Bcl 2 and Bax prot...