摘要：In the previous paper, we reported that ricin and a concanavalin A-ricin A chain conjugate were more toxic to normal cell lines than the transformed variants. In this work, we confirmed this conclusion using other cell lines (KB 3 flat, ST-balb and R4-IudR) which were derived from the Balo/3T3 clone. KN7-8 had a lower number of Con A binding sites than the sensitive parent line (A-31), while the apparent association constant of Con A and surface receptors of KN7-8 was slightly higher than that of A-31. On the other hand, both cell lines had almost the same number of ricin binding sites, while the apparent association constant of KN7-8 was lower than that of A-31. These differences in the number of binding sites and the apparent association constant might not be due to the different sensitivity of these cell lines to the toxin, because the amounts of bound 125I-ricin internalized into the two cell lines during incubation at 37°C were essentially the same. Furthermore, no evidence was obtained showing that there was a difference between A-31 and KN7-8 cells in the ability of reduction of the disulfide bond of ricin, degradation of internalized toxin and in the sensitivity of the protein synthesizing machinery.
