Peixoto de Menezes A, Pinto da Silva P
J Cell Biol. 1978 Mar;76(3):767-78. doi: 10.1083/jcb.76.3.767.
Membrane events during milk fat secretion were analyzed by freeze-fracture of the rat mammary gland. Two modes of milk fat secretion were observed: extrusion of fat droplets surrounded by a portion of the apical plasma membrane of the alveolar epithelial cells and, less frequently, release into the alveolar lumen of fat droplets contained in intracytoplasmic vacuoles. The extrusion process consists of two asynchronous events: clearing of membrane particles (probably including integral membrane proteins) and bulging of the apical plasma membrane. Most fat droplets are extruded with a bilayer membrane envelope (milk fat globule membrane) partially devoid of particles. The segregation of membrane particles may represent the onset of a process of structural degradation of the milk fat globule membrane.
通过大鼠乳腺的冷冻蚀刻技术分析了乳脂肪分泌过程中的膜事件。观察到两种乳脂肪分泌模式:脂肪滴被肺泡上皮细胞顶端质膜的一部分包围并挤出,以及较少见的细胞质内液泡中所含脂肪滴释放到肺泡腔中。挤出过程由两个异步事件组成:膜颗粒(可能包括整合膜蛋白)的清除和顶端质膜的鼓起。大多数脂肪滴被挤出时带有部分缺乏颗粒的双层膜包膜(乳脂肪球膜)。膜颗粒的分离可能代表乳脂肪球膜结构降解过程的开始。