遊離脂肪酸を結合したウシ血清アルブミンを担体とするステロイドホルモンの輸送

抄録

The affinity of bovine serum albumin (BSA) to progesterone, testosterone and androsterone was found to increase significantly by the binding of free fatty acids (FFA) such as myristic acid, palmitic acid and stearic acid, to BSA, while the binding of FFA to BSA affected differently the transport of these hormones through an aqueous membrane containing BSA from a hexane source phase (I) to a hexane receiving phase (II). The main factor governing transport is thought to be the partition coefficient of hormones between the water and hexane phases. The rate constant of hormone transport from the hexane phase (I) to the water phase was defined as k₁ and that from the water phase to the hexane phase (II) as k₂. In the case of a hormone with a lower partition coefficient such as progesterone, the binding of FFA to BSA increased both k₁ and k₂, and accelerated hormone transport. For testosterone with a higher partition coefficient, k₁ did not change, but k₂ decreased to cause decrease in rate of hormone transport. For androsterone with a moderate partition coefficient, k₁ increased, but k₂ decreased so that the binding of FFA had no effect on hormone transport flux.
During transfer from the water to hexane phase (II), the transport rate constant of BSA-binding was 0.050.1 that of the free hormone transport from the water to hexane phase (II) indicating decrease of the rate by the binding of BSA to the hormone. The transport rate constant of BSA-binding was noted to increase for progesterone, to show no change for other hormones by the binding of FFA to BSA.