Morphological and autoradiographical characterization of membrane-like layers surrounding cultured fibroblasts.

Two membrane-like layers of approximately 7 nM thickness were observed in ultrathin cross-sections of flat-embedded cultured fibroblasts. One "membrane", underlying the cell-monolayer, possibly established contacts between cells and substratum. The other "membrane" covered the whole cell culture. These "membranes" were at least partially synthesized by the cells themselves, as was shown by high resolution autoradiography. With regard to our biochemical findings, the autoradiographical results showed that components of these "membranes" consisted of sulfated proteoglycans and may be the morphological equivalent to the biochemically well-defined cell surface associated material, the so-called pericellular pool of glycosaminoglycans.