Singh B, Atwal O S, Minhas K
Department of Biomedical Sciences, University of Guelph, ON, Canada.
J Submicrosc Cytol Pathol. 1995 Apr;27(2):235-49.
Pulmonary intravascular macrophages (PIMs) of sheep have a globular coat on their surface which is mobilized by heparin and halothane, and is implicated in the endocytosis of tracer particles and Escherichia coli lipopolysaccharide. Brefeldin A (BFA) was used in vivo to investigate the effects of a pre-Golgi secretion blocker on the integrity of surface coat, and to know whether PIMs produce coat globules. Sheep were injected intravenously with BFA to reach a one time concentration of 2-5 microgram/ml of plasma, and euthanised at 10, 30, 45, 120 and 180 min (n = 1) post-treatment. Lungs were fixed in situ with 2% glutaraldehyde and 2.5% paraformaldehyde for 30 min. Lung tissues were processed for routine ultrastructural examination including treatment with tannic acid (0.1%), and for the acid phosphatase (ACPase) cytochemistry to identify Golgi complex and enzyme-rich endocytic vesicles. Surface coat was endocytosed by the PIMs within 10 min of BFA treatment through long ACPase-negative endocytic channels and degraded in the acid hydrolase-rich lysosomes. Golgi complex membranes were tubulated and were associated with prominent microtubules, centrioles and secretory vesicles. However, trans-Golgi network was not affected by BFA administration. The coat of PIMs was reconstituted within three hours of BFA-induced endocytosis, in concurrence with signs of enhanced biosynthetic activity. It seems that PIMs do not synthesize the globules, and rather sequester from the plasma to organize a surface coat. It is possible that PIMs contribute a membrane anchor or a receptor to facilitate reconstitution of the coat to perform multiple rounds of globule-mediated cell functions.
绵羊的肺血管内巨噬细胞（PIMs）表面有一层球状被膜，该被膜可被肝素和氟烷激活，参与示踪颗粒和大肠杆菌脂多糖的内吞作用。使用布雷菲德菌素A（BFA）进行体内实验，以研究高尔基体前体分泌阻滞剂对表面被膜完整性的影响，并了解PIMs是否产生被膜小球。给绵羊静脉注射BFA，使血浆中一次性浓度达到2-5微克/毫升，并在治疗后10、30、45、120和180分钟（n = 1）实施安乐死。用2%戊二醛和2.5%多聚甲醛原位固定肺30分钟。对肺组织进行常规超微结构检查，包括用单宁酸（0.1%）处理，以及进行酸性磷酸酶（ACPase）细胞化学检测以识别高尔基体复合体和富含酶的内吞小泡。BFA处理后10分钟内，PIMs通过长的ACPase阴性内吞通道内吞表面被膜，并在富含酸性水解酶的溶酶体中降解。高尔基体复合体膜形成管状，并与突出的微管、中心粒和分泌小泡相关。然而，反式高尔基体网络不受BFA给药的影响。BFA诱导内吞作用后三小时内，PIMs的被膜重新形成，同时伴有生物合成活性增强的迹象。似乎PIMs不合成小球，而是从血浆中摄取以组织表面被膜。PIMs有可能提供膜锚或受体，以促进被膜的重新形成，从而执行多轮小球介导的细胞功能。
