The use of 5-(125I)iodo-2'-deoxyuridine for monitoring DNA synthesis in organ culture.

5-[125I]iodo-2'-deoxyuridine (125IUdR) has been shown to be effective in monitoring DNA synthesis in murine tumour and human benign prostatic hyperplasia explants maintained in organ culture for 2 days, thus making possible the rapid screening of antitumour drugs. Uptake was linear for at least 24 hours in the case of the murine tumour and for 6 hours in the case of the prostate. Hydroxyurea almost completely blocked uptake by the murine tumour at doses above 10(-4) mole. Fluorodeoxyuridine (10(-6) mole) markedly increased the uptake of 125IUdR into the human prostate explants. Fixation of the murine tumour explants in alcoholic Bouin after culture did not alter the radioactive uptake and so routine histological examination of the tissue can be carried out after counting, which is a major advantage over [3H]thymidine.