Ultrastructural Study on Junctional Complexes of the Excurrent Duct Epithelia in the Epididymal Region in the Fowl.

Abstract

Junctional complexes of the epithelia lining the rete testis, efferent ductules, connecting ductules and epididymal duct in the fowl were examined by transmission electron microscopy and by a tracer method using lanthanum nitrate. The junctional complexes were composed of tight junctions, adhering junctions and desmosomes. In the rete testis, one or two points of membrane fusion were observed at the tight junctions. In the efferent and connecting ductules and epididymal duct, the tight junctions consisted of a series of punctate membrane fusions. The adhering junctions and desmosomes showed no remarkable structural differences among these excurrent ducts. Vascularly infused lanthanum nitrate penetrated into the tight junctions of individual epithelia for variable distances, but was prevented from entering the lumen at the site of membrane fusion. These results suggest that the tight junctions can restrict the diffusion of materials via the paracellular route, and that they play an important role in maintaining a suitable fluid environment within the excurrent ducts.