[Mechanism of collagen resorption in uterine postpartum involution].

Extracell and intracell mechanisms of collagen resorption were revealed electron-histochemically in the uterus of rats in its postnatal involution. Cathepsin B secreted mainly by smooth muscle cells as well as by macrophages and fibroblasts into the intracellular space takes an active part in the extracellular collagen resorption. Simultaneously with intensive extracellular lysis of collagen in the uterus there is phagocytosis and intracellular collagen resorption (due to cathepsin B and other lysosomal proteinases) by macrophages and fibroblasts and, to a lesser extent, by smooth muscle cells.