Localization of smooth muscle-like contractile proteins in kidney by immunoelectron microscopy

Contractile proteins of smooth muscle type were found in kidney cells by immunological methods. The reactions of rabbit anti-actin, anti-heavy meromyosin and anti-myosin antisera with rat kidney were investigated by immunoelectron microscopy. Anti-actin stained specifically the foot processes of epithelial cells in the glomerulus, the basal processes of tubular epithelial cells, and the cytoplasm of smooth muscle cells. Anti-heavy meromyosin stained the foot processes at their bases near the cell membrane and close to the basement membrane. Anti-myosin stained the cytoplasm of vascular smooth muscle cells. It is suggested that actin and heavy meromyosin-like proteins may act together to cause movement of foot process cytoplasm.