Abstract
Morphological evidence on lymphatic transport was derived qualitatively and quantitatively in control and volume-expanded rats in order to identify any changes in transendothelial pathways which accompany enhanced lymph formation. Volume expansion was induced by intravenous mannitol and by intraperitoneal hypertonic or hypotonic saline (10% of body wt). Horseradish peroxidase and ferritin were used as macromolecular tracers. Volume expansion had little effect upon intraendothelial cytoplasmic components. Intracytoplasmic vesicles contained tracer molecules in control and experimental groups and quantitative analysis revealed only one significant difference between the groups—a reduction in vesicular volume and numerical densities in animals receiving mannitol. The major changes between control and experimental animals were in the presence of attenuated areas of cytoplasm, widening of intercellular pathways, and the presence of open regions in the expanded group. In these respects there was little qualitative difference among the three experimental groups, although some quantitative differences were recorded. It was concluded that vesicular transport plays a significant role in translymphatic protein movement and that when the interstitial fluid load to lymphatics is increased the excess fluid preferentially enters between adjacent endothelial cells or diffuses across areas of extreme attenuation. Open regions or junctions were considered to play little if any role in lymph formation under control conditions, but to achieve increasing importance with increases in fluid movement.
Published Version
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