INFLUENCE OF TOBACCO-SMOKE ON DNA UNWINDING AND UTEROTROPHIC EFFECT OF ESTROGENS IN RATS

Experiments with a duration of either 3 weeks or 3 months were conduct ed on female rats with initial body weights of 140-170 g. All animals were divided into four groups, i.e. control, tobacco smoke (TS, a whol e-body exposure to the mainstream cigarette smoke), estrogen (EG, diet hylstilbestrol) and TS + EG. Injection of EG started on the day of bil ateral ovariectomy which was performed in all animals 11 days before t he end of the experiment. In shea 3-week experiments TS weakly stimula ted uterine wet weight and in combination with EG significantly increa sed the percentage of intact non-unwound DNA in uterine tissue (stimul ation stage). In the longer 3-month experiments TS decreased a specifi c hormonal effect of EG, i.e. the ability to induce progesterone recep tors in uterine tissue, and did not interfere with the DNA-damaging ef fect of diethylstilbestrol. The conclusion was made that different pha ses exist in hormonal and genotoxic responses to the combined effect o f tobacco smoke and estrogens, which may be related to the mechanisms and types of hormonal carcinogenesis. (C) 1998 Elsevier Science Irelan d Ltd.