Chatterton R T, Harris J A, Wynn R M
J Reprod Fertil. 1975 Jun;43(3):479-84. doi: 10.1530/jrf.0.0430479.
Three specimens were taken from mammary glands of rats killed on the 18th and 21st days of pregnancy and on the 1st day of lactation. Ultrastructural features of the tissue were compared among rats within and between the two stages of development. The similarity among specimens from the same rats made feasible a comparison of serial biopsies obtained every 4 hr, starting on the afternoon of the 21st day of pregnancy. From the 18th to the 21st days of pregnancy, a marked increase in the amount of rough endoplasmic reticulum occurred. The alveolar cells of rats killed on both days and in biopsies obtained at 17 and 13 hr before partuirtion contained abundant small lipid droplets and vacuoles containing many protein granules with little clear fluid (stasis vacuoles). Alveolar lumina were distended with secretion by 17 hr before parturition. Between 8 and 12 hr. before parturition, the accumulated protein and lipid were rapidly extruded from the alveolar cells despite evidence of continued biosynthesis. It is suggested that active transport processes are initiated independently of milk synthesis before parturition.
从妊娠第18天、第21天以及哺乳期第1天处死的大鼠乳腺中采集了三个样本。对两个发育阶段内及阶段间大鼠组织的超微结构特征进行了比较。同一大鼠的样本之间具有相似性，这使得从妊娠第21天下午开始每4小时获取的连续活检样本之间的比较成为可能。从妊娠第18天到第21天，粗面内质网的数量显著增加。在这两天处死的大鼠的肺泡细胞以及分娩前17小时和13小时获取的活检样本中，含有丰富的小脂滴和含有许多蛋白质颗粒且几乎没有清亮液体的液泡（淤滞液泡）。分娩前17小时，肺泡腔内充满分泌物。在分娩前8至12小时之间，尽管有持续生物合成的证据，但积累的蛋白质和脂质仍从肺泡细胞中迅速排出。这表明在分娩前，主动运输过程独立于乳汁合成启动。
