Endothelial cells of arterioles in the stratum vasculosum of the rat myometrium were studied with the electron microscope. Besides a well developed Golgi apparatus, endoplasmic reticulum, centrosomes, cytoplasmic microtubules, and fine filaments, the endothelial cells contain, mostly in their basal portion, a myofibril-like cross-striated fibril. It is composed of filaments of uniform thickness (70 Å) arranged in parallel arrays and forming a bundle with a mean diameter of 0.5 μ. The fibril shows a characteristic cross striation consisting of periodic dense bands (periodicity 0.56 μ) which seem to be similar to the Z-lines of a typical myofibril. Cisternae of the endoplasmic reticulum are frequently associated with the cross-striated fibril. On the basis of various reasons discussed in the text, we consider the fibril as contractile in function and, if its contractile property is proved by other investigations, we propose for the endothelial cells the name "myoendothelium.".
ASJC Scopus subject areas
- Molecular Biology