Changes in the distribution of microtubules in rat Sertoli cells during spermatogenesis

I have studied the distribution of microtubules in rat Sertoli cells during spermatogenesis. The distribution of microtubules was determined by indirect immunofluorescence in fragments of seminiferous epithelium which were mechanically dissociated from perfusion-fixed testes. The presence of microtubules in regions indicated by immunofluorescence was confirmed with electron microscopy. Microtubules are not evident in Sertoli cell regions surrounding early spermatogenic cells, but are abundant in cytoplasm adjacent to apical crypts containing elongate spermatids. In regions surrounding crypts, microtubules are uniformly aligned parallel to the long axis of Sertoli cells. Microtubules in these more central, or columnar, regions of the cells extend from supranuclear levels to the apex of the epithelium. In apical processes surrounding late spermatids, microtubules conform to the contours of the hook-shaped spermatid heads. These microtubules appear continuous with those in the columnar regions of the Sertoli cells. Changes in microtubule distribution observed in the rat are generally similar to, but less elaborate than, those reported previously in the squirrel. These changes may be characteristic of mammalian spermatogenesis in general.