Actin content and organization in normal and transformed cells in culture.

Abstract

The amount of actin and total protein/cell in normal rat kidney (NRK) cells in culture is initially high in very low density cultures, but rapidly decreases as the cells come into contact in higher density cultures. In a viral transformant of NRK (442), the level of actin and total protein does not change significantly from low to high density cultures. NRK cells are flattened against the substrate and have prominent bundles of actinlike microfilaments in the basal cytoplasm adjacent to the substrate. The 442 cells adhere poorly and are more spherical in shape, lacking well-organized basal microfilament bundles, but some may display microfilament bundles in cytoplasmic processes extending from the cell body. The percentage of insoluble actin is < 20% in both cell lines, and 442 cells consistently contain smaller amounts than NRK cells.