Pramila V. Dandekar

The surface coat of epididymal, ejaculated and capacitated sperm

Washed and unwashed epididymal, ejaculated, and capacitated rabbit sperm were incubated for the demonstration of Concanavalin A receptors in the surface coat. In washed cauda epididymal and ejaculated sperm, a uniform, dense layer of reaction product covered the head. The surface coat of the flagellum was thinner and discontinuous. There were no Concanavalin A receptors in the neck. The majority of caput sperm showed no surface reaction. A few were coated with a thin deposit, indicating formation of components containing Concanavalin A receptors. Because unwashed cauda epididymal and ejaculated sperm did not bind to Concanavalin A, it was concluded that receptors were masked by constituents in epididymal and seminal fluid. The plasmalemma of capacitated sperm showed a loss of Concanavalin A binding over the acrosome, beginning at the tip of the head. Shedding of the surface coat may be evidence for membrane alterations during capacitation which prepare sperm for fertilization.