thiouracil and Hemolysis

The ultrastructure of the degradation of red blood cells (RBCs) in vivo by rat thyroid epithelial cells was studied. Two morphologically distinct degradative pathways appeared evident. The granular pathway was characterized by a finely mottled appearance of RBC phagosomes, first observed about the RBC periphery and later extending to the entire RBC matrix. Such phagosomes became gradually smaller, less electron dense, and indistinguishable from cellular lysosomes. The hemolytic degrative pathway was characterized by a progessive, usually homogenous decrease in the density of the RBC matrix except at the periphery of the RBC, where a thin, dense layer persisted for some time. Such phagosomes often appeared swollen relative to freshly ingested RBCs and resembled RBC ghosts. In later stages, they became irregular, smaller, and gradually indistinguishable from cellular lysosomes. Both degradative pathways were associated with ferritin-like particles. The earliest visualization of ferritin was in the cytoplasm, but in later stages it was also found to be concentrated within lysosomes and phagolysosomes.

Topics: Animals; Cytoplasmic Granules; Epithelial Cells; Erythrocyte Membrane; Erythrocytes; Ferritins; Hemolysis; Hemorrhage; Lysosomes; Male; Phagocytosis; Rats; Thiouracil; Thyroid Diseases; Thyroid Gland

A microhemorrhagic process was consistently observed in association with the induction of thyroid hyperplasia by dietary thiouracil in the rat. This process appeared to involve the extravasation of erythrocytes (RBCs) through hyperplastic capillary walls. Those sites of extravasation which were directly visualized involved endothelial openings of less than 1 mu. These openings were surrounded by endothelial cytoplasm containing a dense fibrous material and were associated with RBC constriction during passage. Extravasated RBCs were most often noted singly or in small groups, either in columns between follicular epithelial cells or embedded amongst the basal epithelial infoldings. Occasionally, extravasated RBCs were also observed within follicular lumens. Extravasated RBCs were usually intact ultrastructurally, but occasionally an apparent hemolytic process was observed, both for RBCs embedded amongst epithelial cells and for those within follicular lumens. The nature and etiology of this microhemorrhagic process are considered in relation to the hypervascularity of the gland, the possibility of capillary wall alterations, the presence of endothelial cell mitoses, and the localization of the process.

Topics: Animals; Epithelium; Erythrocytes; Hemolysis; Hemorrhage; Hyperplasia; Male; Rats; Thiouracil; Thyroid Diseases; Time Factors