[Transport of steroid hormones by bovine serum albumin as carrier].

The affinities of bovine serum albumin (BSA) with six kinds of steroid hormones (alpha-estradiol, ethynylestradiol, progesterone, androsterone, dehydroisoandrosterone and testosterone) were studied, and BSA was employed as a carrier to transport these hormones through the liquid membrane system, which consists of a hexane sauce phase (I), a BSA solution phase (1/15 phosphate buffer) and a hexane receiving phase (II). These steroid hormones dissolved in hexane were extensively transferred into a water phase containing BSA compared to the case of control (without added BSA). This suggests that these hormones are bound to BSA in a water phase. The ratio of hormone, BSA-binding form/free-form, is in the following order: ethynylestradiol greater than androsterone greater than testosterone greater than progesterone greater than dehydroisoandrosterone greater than alpha-estradiol in the water phase at the equilibrium conditions. The initial rate of hormone transfer from the hexane phase (I) to the water phase is followed by the first-order kinetics, and BSA induces an increase in the transfer rate except for the case of alpha-estradiol and ethynylestradiol. On the other hand, as for the increase rate of hormone concentration in the hexane phase (II), BSA makes the rate of transfer of progesterone faster than that of control, but it makes the rate of transfer of dehydroisoandrosterone more slowly. The results show the transport behaviors of steroid hormones across a water membrane are governed primarily by the partition coefficient between water and hexane phase and the addition of BSA accelerates the transport of hormones in the case of lower partition coefficients.