The binding of steroid hormones and diethylstilbestrol to proteins of human cells in culture.

The binding of 3H-labeled steroid hormones and a non-steroidal synthetic estrogen, diethylstilbestrol (DES), to proteins of cultured human embryonic lung cells (HEL 299) was studied according to the methods of Diamond et al. [Cancer Res 27: 890-897 (1967)] and Kuroki and Heidelberger [Cancer Res 31: 2168-2176 (1971)]. Ecdysone, estradiol, hydrocortisone, progesterone, testosterone, and DES were selected as test compounds. The aim of this study was to determine the protein binding ability of DES, known as a transplacental carcinogen and teratogen for humans, and to compare it with those of the steroid hormones. DES was bound to proteins to the highest extent, and the amount of binding of estradiol was slightly lower than that of DES. Hydrocortisone, testosterone, and progesterone bound to proteins to smaller extents than DES and estradiol. Very little binding of ecdysone to cellular proteins was detected.