Watanabe S, Sato T
Kanagawa Prefectural Public Health Laboratory, Yokohama, Japan.
Biochim Biophys Acta. 1996 Apr 17;1289(3):385-96. doi: 10.1016/0304-4165(95)00175-1.
Recent studies have shown that, in addition to free steroid hormones, those bound to albumin in plasma may also be available to tissues. In this report, the effects of free fatty acids (FFA) on the binding of steroids to albumin were compared for the cases of bovine serum albumin (BSA) and human serum albumin (HSA). The apparent association constant, Ka, was estimated from the changes in the equilibrium partition coefficient of steroids between the aqueous/hexane phases caused by the addition of albumin to the aqueous phase. In the case of BSA, Ka for progesterone and testosterone increased upon binding of FFA (myristic, palmitic and stearic acid) to BSA and the maximum value of Ka for these steroids could be attained by 3--4 mol of FFA bound per mol BSA. Furthermore, the elution profiles of gel-filtration chromatography clearly showed that progesterone and testosterone are easily liberated from the steroid/BSA complexes and that FFA potentiates the binding of these steroids to BSA. In the case of HSA, the binding affinities of progesterone and testosterone were not greatly affected by bound FFA. On the other hand, the affinities of ethynylestradiol to both BSA and HSA were unaffected below 4 mol of FFA binding per mol.
最近的研究表明，除了游离甾体激素外，血浆中与白蛋白结合的甾体激素也可能被组织利用。在本报告中，比较了游离脂肪酸（FFA）对牛血清白蛋白（BSA）和人血清白蛋白（HSA）情况下甾体与白蛋白结合的影响。表观缔合常数Ka是根据向水相中添加白蛋白后甾体在水相/己烷相之间平衡分配系数的变化来估算的。在BSA的情况下，FFA（肉豆蔻酸、棕榈酸和硬脂酸）与BSA结合后，孕酮和睾酮的Ka增加，每摩尔BSA结合3 - 4摩尔FFA时，这些甾体的Ka可达到最大值。此外，凝胶过滤色谱的洗脱曲线清楚地表明，孕酮和睾酮很容易从甾体/BSA复合物中释放出来，并且FFA增强了这些甾体与BSA的结合。在HSA的情况下，孕酮和睾酮的结合亲和力受结合的FFA影响不大。另一方面，每摩尔结合低于4摩尔FFA时，乙炔雌二醇与BSA和HSA的亲和力均不受影响。
