Interrelationships between germ cell differentiation and transformation of basolateral profile of Sertoli cells during rat spermatogonial cycle.

After treatment with either trypsin, 8N HCl or 5N KOH, or with mechanical dissociation, normally hidden aspects of the seminiferous epithelium were exposed to observation by scanning electron microscopy (SEM). These included the basal surface of seminiferous epithelial cells, the basolateral processes of the Sertoli cell, junctions of the processes, and the basal or adluminal recesses. With the progressing stages of the spermatogonial cycle, three kinds of spermatogonia show different profiles and topographic relations. The basolateral processes of the Sertoli cells can be categorized into four types: conical, wedge-shaped, sheet-like and cup-shaped processes. The first two of the basolateral processes are joined together by close contact and/or overlapping junctions to form the floor of the basal recesses, and they encircle small-sized spermatogonia. The sheet-like processes mutually join by seam line junctions to form the ceiling of the basal recesses. During the spermatogonial cycle, the basal recesses first appear as separated lacunae, then form continuous labyrinth-like trenches, and finally make complicated honeycomb-like lacunae. The cup-shaped processes also are joined by close contact and/or overlapping junctions and are tightly attached by the primary spermatocytes with doughnut-like or linear bodies. The cordal arrangement and adluminal shift of the diverse spermatogonia will be discussed along with the cyclic transformations of Sertoli cell processes and their junctions.