Association between the Doubling Time of Various Cells and Tissues, and the SH-Content of Their Soluble Proteins

The number of SH-groups of the soluble proteins (Prot-SH) of 12 different types of animal tumors and of cultivated chicken fibroblasts increases with decreasing doubling time (id) ■ Between Prot-SH and id an inverse association was found with a significance level of 99.5%. After 30 min incubation in vitro, 4-hydroxypentenal (HPE) reacts with different amounts of the Prot-SH of the investigated cells and tissues. It was found that the absolute, as well as the per­ cental amounts of HPE-reactive Prot-SH increase with decreasing fd > each of the respective inverse associations was found to be highly significant. The tumors were collected in three groups, each with a corresponding range of td and a mean value for Prot-SH. Taking the Prot-SH of the slowest growing tissue (DENA-hepatoma) as the reference value, the increments of Prot-SH were cal­ culated for each of the three groups and were found to be strikingly similar to the number of HPE-reactive Prot-SH. The single Prot-SH increments of the diverse cell and tissue types compared with DENA-hepatoma were found to be highly significantly and inversely associated with the respective Prot-SH decreases caused by HPE. Hence it may be concluded that HPE reacts preferably with those of the Prot-SH which are of some functional importance for tumor growth and, moreover that the attack on those thiols is the more effective the faster the tumor is growing.