Ultrastructural observations on spermatozoa retained within the seminiferous epithelium after treatment with dibutyryl cyclic AMP.

Spermiation was inhibited in the Syrian hamster by administering large doses of dibutyryl cyclic AMP. After treatment with dibutyryl cyclic AMP most stage VIII, IX, and X seminiferous tubules contained some mature spermatozoa within the seminiferous epithelium. The acrosomal membranes and plasma membranes of the unreleased spermatozoa remained intact, indicating that the spermatozoa had not been phagocytized by the Sertoli cells. Sertoli-spermatid junctional specializations were usually applied to the heads of the mature spermatozoa. The unreleased spermatozoa often appeared swollen with accumulated fluid located in the subacrosomal space. The accumulation of subacrosomal fluid in the unreleased spermatozoa seems to result from the absence of tubulobulbar complexes. That is, when tubulobular complexes fail to form the normal flow of cytoplasm into the tubulobular complexes is blocked resulting in an accumulation of fluid around the nucleus. Inhibition of spermiation may result from the absence of tubulobulbar complex formation. It is postulated that the tubulobulbar complex functions to transfer a chemical trigger from the maturing spermatid into the Sertoli cell. This chemical trigger may initiate the disappearance of the Sertoli-spermatid junctional specialization and induce spermiation.