Yokomuro S, Kudou M, Onda M, Asano G
Department of Pathology, Nippon Medical School, Tokyo, Japan.
J Surg Res. 1993 Sep;55(3):290-4. doi: 10.1006/jsre.1993.1142.
Lecithin and bile acid form mixed micelles in the bile. We found that the mixing ratio in lecithin/bile acid mixed micelles directly changes the activity of Na(+)-K+ ATPase. Na(+)-K+ ATPase activity was suppressed to 13.3% of that in the buffer alone at a lecithin/bile acid mixing ratio of 0.1 in the presence of 10(-2) M bile acid (that is, a concentration level close to that of the hepatic bile). With increase in the mixing ratio in the presence of 10(-2) M bile acid, the activity of the enzyme was found to be augmented accordingly. Thus addition of lecithin to an extent such that the mixing ratio reached 0.6 led to an enhancement of enzymatic activity to 193.8%. If lecithin addition is made in the presence of bile acid at the near gallbladder concentration of 10(-1) M, however, the Na(+)-K+ ATPase activity can be observed to increase with the increase in the lecithin/bile acid ratio. Yet, at the same mixing ratio of 0.6, the enzyme activity was arrested at only 25.7%. However, this change in mixing ratio had no effect on ouabain-insensitive ATPase. The state of mixed micelles may exert the same effect on Na(+)-K+ ATPase activity in vivo.
卵磷脂和胆汁酸在胆汁中形成混合微团。我们发现，卵磷脂/胆汁酸混合微团中的混合比例直接改变钠钾ATP酶的活性。在存在10⁻² M胆汁酸（即接近肝胆汁的浓度水平）的情况下，当卵磷脂/胆汁酸混合比例为0.1时，钠钾ATP酶活性被抑制至仅为单独缓冲液中活性的13.3%。在存在10⁻² M胆汁酸的情况下，随着混合比例的增加，该酶的活性相应增强。因此，添加卵磷脂使混合比例达到0.6时，酶活性增强至193.8%。然而，如果在接近胆囊浓度10⁻¹ M的胆汁酸存在下添加卵磷脂，钠钾ATP酶活性会随着卵磷脂/胆汁酸比例的增加而增加。然而，在相同的0.6混合比例下，酶活性仅停滞在25.7%。但是，这种混合比例的变化对哇巴因不敏感的ATP酶没有影响。混合微团的状态可能在体内对钠钾ATP酶活性产生相同的作用。
