Behavior of fluorescent granular perithelium (FGP) in cerebral cortex of SHR-SP rats under some conditions.

The fluorescent granular perithelial cells (FGP) in control and experimental specimens of SHR-SP rats were studied with light and electron microscopes. The results obtained are as follows. The FGP in SHR-SP rats are localized along small cerebral vessels and provided with many irregularly shaped inclusion bodies. Their matrices are homogenous and relatively less dense. Sometimes, the FGP fall into degeneration and their cytoplasm shrinks and fills with small dense granules. Concomitantly, collagen fibers appear surrounding them. After feeding rats a fat-rich chow, lipoidal substances appear in intracellular granules of FGP at the light microscopical level. Electron microscopically, the FGP are swollen and their inclusion bodies vary in shape and content. Large inclusion bodies are composed of several middle-sized inclusion bodies with heterogenous matrices. Frequently, pale inclusion bodies are provided with intensely stained limiting membranes. These facts suggest an incorporation of fat into the FGP. With the administration of elastase, intracellular lipid decreases moderately and the FGP scarcely swell. The cytoplasm of FGP and the contents of inclusion bodies become defined and contrasty. From this evidence, elastase seems to facilitate a fat metabolism in FGP. Morphological and functional differences between FGP and other perivascular cells including pericytes, microglia, and mast cells are briefly discussed.