Transplacental carcinogenesis with radioactive phosphorus: the effects of promoting agents

In a previous experiment, using 32P as a potential transplacental carcinogen in rats, we found that the isotope caused life-span shortening, reduced growth and caused ante-dating of the time of the tumour occurrence. Liver cell changes (nuclear atypia, variation in cell size) were noted and suggested liver cell damage, possible 'initiation'. A phorbol ester (TPA) and a high fat/high protein diet were used as promoting agents on further transplacentally irradiated rats. The results were identical to the previous experiment; no evidence of promotion was found.