Meddings J B
University of Calgary, Health Sciences Center Intestinal Disease Research Group, Alberta, Canada.
Biochim Biophys Acta. 1989 Sep 4;984(2):158-66. doi: 10.1016/0005-2736(89)90211-3.
Fatty acids and cholesterol permeate across the intestinal microvillus membrane at rates dictated by the hydrophobicity of the permeating lipid and the permeability properties of the microvillus membrane. A theory has evolved suggesting that the chemical composition and physical properties of the microvillus membrane are important in determining microvillus membrane lipid permeability in vivo. This communication reports a test of this hypothesis. To compare in vivo membrane lipid permeability within the same intestinal region, but under conditions were membrane physical properties were radically altered, rats were fed an inhibitor of cholesterol synthesis. This resulted in the replacement of 87-90% of membrane cholesterol with its' precursor, 7-dehydrocholesterol. Marked changes in membrane physical properties were observed, including a reduction in the static and dynamic component of membrane fluidity within the jejunal microvillus membrane. These changes were limited primarily to the outer regions of the bilayer. Associated with these alterations was a pronounced reduction in membrane lipid permeability. Therefore, microvillus membrane lipid permeability, in vivo, appears to be correlated with physical properties of the bilayer, especially those of the superficial regions.
脂肪酸和胆固醇以由渗透脂质的疏水性和微绒毛膜的通透性所决定的速率穿过肠道微绒毛膜。一种理论逐渐形成，表明微绒毛膜的化学组成和物理性质在决定体内微绒毛膜脂质通透性方面很重要。本通讯报道了对这一假设的检验。为了比较同一肠道区域内但在膜物理性质发生根本改变的条件下的体内膜脂质通透性，给大鼠喂食胆固醇合成抑制剂。这导致膜胆固醇的87 - 90%被其前体7 - 脱氢胆固醇取代。观察到膜物理性质发生了显著变化，包括空肠微绒毛膜内膜流动性的静态和动态成分降低。这些变化主要局限于双层膜的外层区域。与这些改变相关的是膜脂质通透性明显降低。因此，体内微绒毛膜脂质通透性似乎与双层膜的物理性质相关，尤其是表层区域的物理性质。
