Changes in the Golgi apparatus during spermiogenesis in the rat

The fine structure of the Golgi apparatus in rat spermatids at various steps of spermiogenesis was investigated in routinely stained preparations as well as in sections stained with the periodic acid‐silver technique for the demonstration of glycoprotein. In steps 1–7 spermatids, a layer of cisternae of endoplasmic reticulum envelops the Golgi apparatus. Between this layer and the stack of Golgi saccules, small coated vesicles (500–600 Å) are associated with smooth‐surfaced tubular profiles. These are irregular expansions of the first or outermost Golgi saccule. The next few saccules of the stack are regularly arranged and similar to one another. The last or innermost saccule is thick and produces coated buds, similar to the large coated vesicles (900–1200 Å) which are found nearby. Large smooth vesicles with a dense core, known as proacrosomic vesicles, are also found in this location at steps 1 and 2. These at step 3 fuse into the single acrosomic vesicle, which in turn at step 5 transforms into the head cap (while the dense core of the vesicles becomes the acrosomic granule). Using the PA‐silver technique on steps 1–7 spermatids, a gradation of staining is observed in Golgi saccules, with the most intense reaction in the innermost saccule, its coated buds and the large coated vesicles nearby. Intense staining is also noted in the head cap, while staining of lesser intensity is observed in the acrosomic granule. In older spermatids (steps 8–18) the Golgi apparatus gradually loses most of the features just described and appears to consist primarily of stacks of saccules with dilated edges. These are only weakly stained by the PA‐silver technique. These observations are interpreted as follows. Material produced in the endo‐plasmic reticulum would be transferred by small coated vesicles to the outermost saccule of the Golgi stacks. During saccule migration toward the inner aspect of the stacks, the synthesis of glycoprotein would be completed. The transfer of this glycoprotein via the large coated vesicles would cause the proacrosomic vesicles to grow into the acrosomic vesicle which later would become the head cap.