Phillips J H
Biochem J. 1977 Nov 15;168(2):289-97. doi: 10.1042/bj1680289.
'Ghosts' of bovine chromaffin granules, in which the complex mixture of proteins and solutes normally found in the granule matrix is replaced by buffered sucrose are osmotically sensitive. They shrink when the osmotic pressure of the suspension medium is increased, and swell if solute entry is facilitated by the addition of ionophores. Swelling in the presence of ionophores has been used to investigate the passive ion permeability of these membranes. They have a very low permeability to K+ ions (of the order of 10(-10) cm/s); their permeability to protons, Na+ and choline ions is too low to be detected by these methods. Their passive permeability to anions decreases in the order: CNS- greater than I- greater than CCl3CO2- greater than Br- greater than Cl- greater than SO4(2)- greater than CH3CO2-, HCO3-, F-, PO4(3)- the permeability to hiocyanate being of the order of 10(-7) cm/s. Coupled proton and anion entry is extremely slow, except for weak acids. Fluoride, unexpectedly, also appears to enter rapidly when proton/K+ exchange is facilitated by nigericin. In the presence of K+ salts, nigericin, like valinomycin, induces lysis of intact granules, an effect that is not dependent on the presence of a permeant anion, but is dependent on the pH gradient across the membrane.
牛嗜铬颗粒的“幽灵”，即颗粒基质中通常存在的蛋白质和溶质的复杂混合物被缓冲蔗糖取代后，对渗透压敏感。当悬浮介质的渗透压增加时它们会收缩，而如果通过添加离子载体促进溶质进入则会膨胀。在离子载体存在下的膨胀已被用于研究这些膜的被动离子通透性。它们对K +离子的通透性非常低（约为10（-10）cm/s）；它们对质子、Na +和胆碱离子的通透性太低，无法用这些方法检测到。它们对阴离子的被动通透性按以下顺序降低：CNS-＞I-＞CCl3CO2-＞Br-＞Cl-＞SO4(2)-＞CH3CO2-、HCO3-、F-、PO4(3)-，对硫氰酸盐的通透性约为10（-7）cm/s。除了弱酸外，质子和阴离子的耦合进入极其缓慢。出乎意料的是，当尼日利亚菌素促进质子/K +交换时，氟化物似乎也会迅速进入。在K +盐存在下，尼日利亚菌素与缬氨霉素一样，会诱导完整颗粒的裂解，这种效应不依赖于渗透性阴离子的存在，而是依赖于跨膜的pH梯度。
