SURFACE AND SURFACE-TO-VOLUME RELATIONSHIPS OF THE SERTOLI-CELL DURING THE CYCLE OF THE SEMINIFEROUS EPITHELIUM IN THE RAT

The surface relationships of the Sertoli cell and the surface relation ships of the Sertoli cell in comparison to the changing volumes of dev eloping germ cells were studied using morphometric techniques at perio ds representing nine groupings of the fourteen defined periods in the cycle of the seminiferous epithelium of the adult rat. No cyclic varia tion in the total Sertoli plasma membrane surface area was noted. Cycl ic variations were noted in the area of the Sertoli cell surface that faces the basal compartment germ cells, but not the basal lamina. No c yclic variations were noted in the amount of contact of the Sertoli ce lls with each other at the level of the Sertoli cell barrier. However, when areas in the adluminal compartment were studied, significantly l ess Sertoli-Sertoli contact was seen in stages V through VII than in o ther stages with the exception of stages II-IV. Surface contact of ger m cells with Sertoli cells increased progressively as germ cells enter ed the intermediate compartment and progressed to late spermatids. How ever, a calculation of the surface-to-volume ratio showed that surface increases of the Sertoli cell in relation to the volume of germ cells were greatest in elongating spermatids past step 12 of spermiogenesis . The area in which Sertoli ectoplasmic specializations faced germ cel ls was determined throughout spermatogenesis, and these data demonstra ted that the first appearance of ectoplasmic specialization was at the mid-pachytene phase. They also showed that stage VIII was a period wh en ectoplasmic specialization loss from the cell surface was evident. Less Sertoli ectoplasmic specialization faced step 8 and step 19 sperm atids than comparable germ cell types at other stages. In addition to Sertoli cell surface area changes during the cycle, volumes of individ ual germ cell types were determined for the first time. The data prese nted allow an objective understanding of the complex structure and rel ationships of the Sertoli cell and provide a basis for understanding f unctional changes and interpreting biochemical data.