Epididymal Maturation of Rat Spermatozoa Studied by Thin Sectioning and Freeze-Fracture

Abstract

Rat spermatozoa in various segments of the epididymis were studied by thin sectioning and freeze-fracture. In the initial segment of the epididymis, a flocculent material fills the space between the plasma membrane and outer acrosome membrane. This disappears in the more distal segments. As spermatozoa move into the middle of the caput epididymidis, a variable glycocalyx material (VGM) accumulates upon the outer surface of the plasma membrane covering the acrosome. In the distal caput, VGM begins to separate and becomes completely detached in the proximal cauda. As seen by freeze-fracture, the particles of the plasma membrane covering the acrosome change their arrangement during epididymal passage. A hexagonal arrangement of these particles was noted in spermatozoa from the middle of the caput, but the array became disorganized as the spermatozoa moved through more distal parts of the epididymis. The relations of VGM on the plasma membrane with the particles changed during maturation.