Synthesis of type III collagen by cultured kidney epithelial cells.

Studies have been performed to evaluate both the relative amounts and molecular forms of the collagens synthesized by an established line of cultured rat kidney epithelial (clone NRK52E) cells. The collagens secreted into the culture medium and extracted from the cell layers of cultured NRK52E cells were isolated after limited pepsin digestion and differential salt fractionation. Greater than 95% of the collagenous proteins synthesized by NRK52E cells were found to be associated with the cells and not secreted. Polyacrylamide gel electrophoresis under denaturing conditions of the NRK52E cell collagens indicated the presence of components exhibiting properties corresponding to those of the chains present in types I, III, IV and V collagen. Analysis of each fraction by carboxymethyl-trisacryl chromatography revealed that approximately two-thirds of the total collagen synthesized by NRK52E cells was type III. Of the remaining collagen types I, IV and V molecules represented 20%, 4% and 10% respectively, of the total produced. Essentially all of the type I collagen produced by NRK52E cells was recovered as the type I-trimer, whereas the type V molecules synthesized by NRK52E cells had the molecular compositions of [alpha 1(V)]2 alpha 2(V) and alpha 1(V)alpha 2(V)alpha 3(V). These data establish the relative proportions and molecular forms of the collagens synthesized by cultured NRK52E cells. Furthermore, these findings suggest that NRK52E cells may be a useful in vitro model for investigating the regulation of changes in collagen biosynthesis occurring under situations of renal epithelial cell injury.