Changes of enzymic activities in human diploid cell line WI-38 at various passages

Three groups of enzymes, namely, phosphatases, dehydrogenases and transaminases have been studied in the development of human diploid cells, WI-38, from passage 20 to passage 52. There was a general decrease in the activities of these three groups of enzymes after passage 42 and some increases of enzymic activities in the 31-42 passage range. The total cellular proteins were generally constant from the 20th to the 48th passage and increased after passage 48. However, an increase of protein in a specific cellular fraction at certain passages was observed. From pH and inhibitor studies on WI-38 diploid cells, malate dehydrogenase showed a shift to a high pH optimum at later passages, while acid phosphatase has shown no change to inhibitors from early to later passages. However, sodium tartrate showed an increased inhibitory effect on the soluble Zn²⁺-activated acid phosphatase as passages progressed. Decreased inhibitory effect by cysteine and cyanide on alkaline phosphatase has been observed in the later passages.