Unconjugated estradiol in the myometrium of pregnancy.

By chemically digesting myometrium in a mixture of NaOH and sodium dodecyl sulphate, estradiol could be recovered almost completely by extraction with ethyl acetate. The concentration of estradiol-17beta (E2) in the extracted samples could reliably be determined by radioimmunoassay. Compared to its concentration in the plasma, E2 in the pregnant human myometrium was very low, and as a result, the tissue/plasma estradiol concentration ratio was less than 0.5. In the pseudopregnant rabbit, this ratio ranged between 16 and 20.