Actin filaments in retinal pericytes and endothelial cells

The contractile protein actin was identified within retinal capillary pericytes and endothelial cells. In capillary cross-sections, circumferential pericyte processes showed numerous parallel bundles of actin filaments forming a cap over the adjacent endothelial cells. The latter contained few actin filaments but a considerable number of intermediate filaments. Pericytes and endothelial cells communicated via gaps in the adluminal basal lamina. These special anatomic relationships are interpreted as evidence for a contractile role of retinal capillary pericytes and against a contractile role of retinal capillary endothelial cells