Erythrophagocytosis by brown adipocytes of rat interscapular tissue.

In this investigation the following phenomena were observed: 1. Rat interscapular brown adipocytes were found to be capable of erythrophagocytosis; 2. Before leaving the capillary lumen, erythrocytes took some material from the blood plasma by endocytosis and passed the endothelial junction carrying endocytotic vacuole. Some erythrocytes were in transit: the so-called "head" was in the process of engulfment by brown adipocytes while the rest of the cell had not left the capillary lumen. Fragmentation of erythrocytes was observed during passage through the endothelial junction as well as in the cytoplasm of adipocytes. 3. In some brown adipocytes erythrocytes retained the same shape as in the capillary, but in many cases they exhibited unusual form. Intracytoplasmic erythrocytes were seen in a semithin sections stained with toluidine blue. 4. Erythrocytes either became cells which phagocytized mitochondria and lipid droplets before their transformation into lipofuscin bodies or they were degraded into ferritin-like particles observed (on unstained sections) in the mitochondrial matrix, intercristal space, on the periphery of lipid droplets and in brown adipocyte cytoplasm.