Scanning electron microscopic study of arterial cushions in rats: a novel application of the corrosion-replication technique.

The morphology and organ distribution of arterial cushions were studied in adult rats (body weight ranging from 200 to 500 gm) by scanning electron microscopic (SEM) observation of corrosion casts. Scanning electron microscopic observations of renal vascular casts were correlated with SEM views of the luminal surfaces of similarly fixed vessels; there was a striking similarity in shape, organ distribution, and dimensions between fixed arterial cushions and indentations at the surfaces of casts. Application of this technique to 11 different organs, some of which had never been studied by SEM before, revealed the occurrence of indentations at branching sites similar to those found in kidneys (and hence they were termed "cushions"). Our findings are in generally good agreement with previous light and transmission electron microscopic studies on rats. Our results support the view that arterial cushions are present throughout the vasculatures of the rat. A quantitative morphologic study of replicated branching sites related to "cushions" showed a great variability of the parent-to-daughter luminal diameter ratio (range 0.87-16.38) and of branching angles. A fruitful application of this technique to other laboratory animals may be anticipated.