Studies of the guinea pig epididymis. II. Intercellular junctions of principal cells.

The junctional complexes of the principal cells in the guinea pig epididymis were analyzed using freeze fracture and ultrathin section goniometric techniques. Replicas of the seven regions (I to VII) investigated reveal a continuous decrease in the number of tight junctional strands, ranging from 15.73 +/- 3.54 in zone I (proximal) to 4.39 +/- 0.78 in zone VII (distal tubule). The distance from the adluminal to the basolateral strand also diminishes from proximal, 0.73 +/- 0.02 micron to distal, 0.19 +/- 0.03 micron. The junctional strands appear on the P-face and anastomose forming compartments which are larger in the basolateral areas than those in the apical. The network of strands frequently form terminal loops and blind endings towards the more basal parts of the lateral membrane. Freeze fracture images also exhibit randomly distributed particulate aggregations which correspond to maculae adhaerentes, the highest number of which are found in zone IV, V, and VII. Desmosomal figures are found not only below, but also adjacent and intermingled among the tight junctional strands. This special junctional arrangement is confirmed upon goniometric analysis of ultrathin sections from zones IV, V, and VII. Electron dense desmosomal plaques are seen parallel and directly subjacent to the membranes of the tight junctions, following the strands in both directions to finally converge on the punctiform connections. Goniometry also reveals a dense feltwork of material closely applied along the lateral cell border. These zonulae adhaerentes are seen to be of greatest length and density in zones I, VI, and VII.