Influences of age and vasopressin on the uptake capacity of fluorescent granular perithelial cells (FGP) of small cerebral vessels of the rat.

Fluorescent granular perithelial cells (FGP) were found in the perivascular space around fine cerebral blood vessels. Their profiles and intracellular inclusions varied with the age of the animals. The FGP are able to take up exogenous substances administered intraventricularly. With light and electron microscopy, the relation between the uptake capacity of FGP and the aging of animals was studied using horseradish peroxidase (HRP). The effects of vasopressin on the uptake of HRP also were examined. The results can be summarized as follows: 1) The uptake capacity of FGP diminished with aging, that is, the reaction product of administered HRP was found abundantly in FGP in young rats, while it was sparse in the FGP of old rats and 2) vasopressin increased the incorporation of HRP into the FGP of both young and old rats. The possible role of vasopressin in modulating the uptake capacity of FGP is considered, and the difference between FGP and other perivascular cells are discussed.