Prevention of mammary @entity105 in XXXX by pregnancy: effect of full-term and interrupted pregnancy.

@entity3653 @entity894 @entity5 @entity665 @entity106 @entity35 @entity105
In this study, the role of parity in conferring protection of the mammary gland against @entity105 induced by @entity3653 ( @entity106 ) was investigated. Experiments were also carried out to determine if an 'interrupted' pregnancy was capable of reducing the incidence of mammary @entity5 induction. Since it has been suggested that morphological development or the proliferative pattern of the mammary gland at the time of carcinogen administration may be involved in reducing the susceptibility of the mammary gland to @entity105 , experiments were designed to elucidate the possible influence of these two factors. Sprague-Dawley female @entity35 were mated and were either allowed to complete pregnancy and parturition or were subjected to Caesarian section on day 5, 10 or 15 of the pregnancy. When @entity106 was administered i.v. to animals which had been allowed to complete a full-term pregnancy, only 14% developed @entity5 , compared to 70% in age-matched nulliparous controls. Termination of the pregnancy on days 5, 10 or 15 was as effective in reducing @entity5 incidence as full-term gestation and parturition, but still resulted in partial and statistically significant inhibition, compared to age-matched nulliparous controls. There was no significant difference in @entity665 @entity894 ( @entity894 ) at the time of @entity106 treatment in the parous @entity35 compared to age-matched nulliparous controls. We also observed no significant differences in the morphological development of the mammary gland in parous and nulliparous @entity35 of the same age. These results indicate that the protective mechanism may not lie in the mammary gland per se, but may indeed be a host factor, such as hormonal or immunological changes occurring in the host as a result of the pregnancy.
