Effects of colchicine administration on the endothelial cells of the developing semilunar heart valves of the chick embryo.

Recent ultrastructural studies have revealed that differences exist in endothelial cell shape and cytoskeletal architecture between the arterial and ventricular faces of developing semilunar valves. In the present work we analyzed the morphologic response of the valvular endothelial cells of chick embryos to colchicine by light microscopy, scanning electron microscopy and transmission electron microscopy. The results show that colchicine administration during the stages of valve morphogenesis causes a very conspicuous disruption of the endothelial layer of the arterial face of the valves. The cells appear rounded and show massive surface blebbing. These alterations were not present in the endothelial cells on the ventricular face of the valves at the same stages. On the basis of these results we suggest that a difference in the degree of cell differentiation exists between the endothelial cells of the arterial and ventricular faces of the cusps and that this difference may have morphogenetic significance.