A simple and sensitive microtiter plate estrogen bioassay based on stimulation of alkaline phosphatase in an endometrial adenocarcinoma cell line (Ishikawa line).

We have developed an estrogen bioassay using the Ishikawa human endometrial adenocarcinoma cell line grown in 96-well microtiter plates. Alkaline phosphatase enzyme activity (Alkp) in these cells was markedly stimulated by estrogen (E2), and this enzyme can be easily quantified in situ using a chromogenic substrate. Estradiol induces AlkP at levels as low as 10-8M. The induction of AlkP is specific for estrogens as for other steroids and other steroidal materials (Progesterone, Tamoxifen, clomiphene citrate, Ru 486, ICI) could not produce a similar effect. The stimulation of AlkP in Ishikawa cells is not only specific for estrogen, it is highly reproducible and sensitive and permits large numbers of samples to be assayed with ease. The non-radioactive nature of the assay makes it attractive to developing countries.