Application of an ELISA procedure for the quantitation of bromodeoxyuridine incorporated into cellular DNA.

We have developed a sensitive enzyme-linked immunosorbent assay (ELISA) procedure that uses a commercially-available anti-BrdUrd antibody for the quantitation of BrdUrd substituted into DNA. In our assay, 50% displacement occurs at 0.89 nM of BrdUrd in 2.2% BrdUrd-substituted DNA, which is equivalent to 2.47 ng of BrdUrd-containing DNA. A fluorescein isothiocyanate-conjugated anti-BrdUrd antibody was used to determine the labeling index of cultured cells and in vivo tumors treated with BrdUrd. Combining results of the ELISA procedure (to determine the percent BrdUrd substitution), and flow cytometry (to determine the percentage of cells that incorporated BrdUrd) we found that BrdUrd incorporated into the DNA of cells in vitro and tumors in vivo could be quantitated with precision.