Characteristics of cultured subepithelial fibroblasts of rat duodenal villi.

Subepithelial fibroblasts, which form a cellular network beneath the epithelium of rat intestinal villi, were cultured, and their morphological characteristics were examined. These fibroblasts, which migrated from epithelium-free villi (isolated primarily from duodenum) were flat in shape after 2 days of culture. The flat cells, each resembling a maple leaf, were rich in bundles of microfilaments, and were connected to each other by a few small gap junctions, ascertained from freeze-fracture and dye-coupling experiments. The morphology of the flat cells changed to a stellate form, with thin processes, within 30 min-1 h of reducing the serum concentration and adding dibutyryl cyclic AMP (dBcAMP), forskolin, and cholera toxin. Upon removal of dBcAMP and addition of fetal calf serum, the cells rapidly reassumed their original flat shape. Cells that were stellate in the presence of dBcAMP reassumed a flat morphology within several minutes after the addition of endothelin-1. This conversion occurred with or without extracellular Ca2+. An accompanying rearrangement of the cytoskeleton during shape conversion was observed by fluorescence immunohistochemistry.