Actin like filaments in the peritubular cells of human testis chemical extraction and binding with heavy meromyosin.

Two types of the cytoplasmic filaments are found in human peritubular cells; thin filaments (50-80 A) and 100 A filaments. The thin filaments are numerous and tightly packed in cytoplasma of peripheral cell processes, and form bundles. These bundles are arranged in parallel with the long axis of the cells. Dense areas are occasionally seen among the filaments, or underneath the cell membrane to which the thin filaments seem to be anchored. The 100 A filaments are generally located around the perinuclear region or in the middle region of cytoplasma. The thin filaments are not altered after incubation with Hasselbach-Schneider's solution. These filaments, however, disappear in cytoplasma when extracted with 0.6 M KI solution. And also, the thin filaments form chracteristic arrowhead complexes, when incubated with HMM, while these complexes are never found, when incubated with HMM plus ATP. The 100 A filaments do not react to HMM. Thus it is suggested that the thin filaments are actin or actin like and that a contractile system exists in human peritubular cells, which may be involved in transport of nonmotile sperm or permeability of the seminiferous walls.