Ultracytochemical study of multiple dose effect of monastral blue uptake by equine pulmonary intravascular macrophages (PIMs).

The pulmonary intravascular macrophages (PIMs) of the ponies possess all the characteristics of a fully differentiated resident macrophage, which forms adhesive plaques with the capillary-endothelial cells. In addition, it has a unique surface coat which does not conform to the concept of a carbohydrate rich membrane bound glycocalyx generally associated with macrophages. We studied the responses of these cells especially in the context of its globular surface coat to multiple doses of MB intravenously: 0.2 ml/kg body copper tracer substance. The ponies were treated with three doses of MB intravenously: 0.2 ml/kg body weight on day 0, 0.1 ml/kg at 48 h and a 0.05 ml/kg at 96 h after the first dose. The examination of lung tissue at the ultrastructural level revealed internalization of MB following complexing with the surface coat globules along the entire cell surface. The cell surface was extensively ruffled in the form of several lamellipods. The MB-globule complex was internalized mostly at the coated pits whereas concurrent internalization of nascent globules of the coat took place at the ruffled surface. In the former, the internalized material was seen in small, medium and large phagolysosomes which stained intensely for acid phosphatase, whereas in latter case enzyme activity was entirely absent in all the nascent globules carrying endosomes. Simultaneously there was hypertrophy of the Golgi complex, which showed intense staining for acid phosphatase. Relative to the Golgi response, acid phosphatase-positive tubular lysosomes in close association with extensive bundles of microtubules were conspicuous, thus adding to the battery of cell organelles of secretory pathway.(ABSTRACT TRUNCATED AT 250 WORDS)