[In vitro resistance testing of tumors in relation to cytostatics. 1. Animal experiments]

By studying rat Yoshida sarcoma and Walker carcinoma, pertinent results have been obtained for chemotherapy drug (CD) resistance of human tumors. The incorporation rates of tritiated metabolic precusors of DNA and RNA synthesis could be shown to be reproducible in ascites tumor cells and in solid tumor cells, in the absence as well as in the presence of CDS. Fraction of proliferation cells, cell cycle phase duration and tumor generation time were equal before and after explanation. The in vitro CD concentration used did not promote cell death within the first 4 h post-explantation, as shown by supravital stain (with Lissamin green and Trypan blue) and by 51Cr-release studies.