Figure 1From: Interspecies differences in membrane-associated protease activities of thyrocytes and their relevance for thyroid cancer studiesDetection of protease activity with synthetic substrates by histochemistry (red) in porcine (a, c) and bovine (b, d) thyroid tissue. Activities of perifollicular cells (endothelial cells, fibroblasts and C-cells) for the respective proteases are indicated by arrowheads. a, b: Activity of dipeptidyl peptidase II is seen intracellularly in thyrocytes of both species. c: In porcine thyroids activity of dipeptidyl peptidase IV is seen in some follicle cells. d: In bovine thyroids, follicle cells show no activity for dipeptidyl peptidase IV substrate. e: Activity of aminopeptidase N is seen at the apical part of the cells in porcine follicular thyrocytes (arrow), whereas in bovine thyroids (f) activity of aminopeptidase N is restricted to endothelial cells the perifollicular stroma below the follicular epithelium (arrowhead). FL: follicle lumen.Back to article page