The response of rats to the simultaneous application of two different carcinogenic agents.

The present study was undertaken to investigate the carcinogenic reaction of rats trcated with two different and differently acting carcinogens. This seemed to be of interest for various reasons. First, it would be possible to study the influence of one carcinogenic agent on the action of another. Although there are numerous publications on the action of carcinogenic substances on established tumors, transplanted and spontaneous, the interaction of two differently acting chclnical carcinogens has, as far as we know, not yet been studied. The second reason is that it may be possible to decide whettler in the anlma]s susceptible to the action of one carcinogen there exists a predisposition for developing also the type of tumors characteristic for the second agent applied at the same time, e.g. whether a rat that will develop a hepatic tumor by the action of ~-dhnethylaminoazobenzene is more susceptible to the effect of methylcholanthrene than one that resists the carcinogenic diet. The experiments were made with albino rats of our own unsclccted breed, which has a relatively high incidence of spontaneous tmnors. Such a strain seemed more suited for this study than a highly selected one, in which response to carcinogenic stimuli and localization of induced tumors are influenced by artificially selected genetlcal factors. It may be assumed certain differences in reaction to carclnogcnic stimulation exist in these unselected animals, which should be revealed by the experiments. Moreover, it should be possible to observe the effect of specific carcinogenic agents on the incidence of spontaneous tumors.