Inhibition of DNA Synthesis by an Extract From Human Placenta 1, 2

SUMMARY-A water extract of human placental membranes inhibited DNA synthesis and cell division in fibroblasts, lymphocytes, and epidermis. The effect occurred rapidly and was abolished by heating at 60 ° C. Gel filtration studies indicated the inhibitor had a molecular weight of about 70,000. Storage in aqueous solutions and treatment with trypsin resulted in marked loss of activity. No significant inhibition of RNA or protein synthesis could be demonstrated. The inhibitor did not exhibit cytotoxicity as judged by cytologic criteria and uptake of trypan blue, but cell death did occur after prolonged exposure.-J Nat