Distribution of transglutaminase in quail uropygial glands

The holocrine secretion of the uropygial gland has been explained as autolysis due to intracellular lysosomal enzymes. In the present study, the distribution of transglutaminase, a marker of epidermal differentiation, in quail uropygial glands was observed by histochemical methods to confirm whether a mechanism similar to epidermal differentiation also exists in the uropygial gland. The transglutaminase activity was positive in the deep and shallow portions of the secretory tubules as well as the transitional and degenerating cell layers of the uropygial gland. This activity was stronger in the deep portions than the shallow portions. These findings suggest that the process of secretion in the quail uropygial gland involves not only the autolysis due to lysosomal enzymes but also a mechanism similar to that of epidermal differentiation, and that a phenomenon similar to epidermal differentiation is more evident in the deep portions than the shallow portions.