Binding of 2D6-Reactive Antigens to the Sperm Plasma Membrane
In nearly all examples of secreted epididymal glycoproteins binding to the sperm surface, only qualitative information is available, whereas in the present work we have used FACS analysis to quantify the interaction between 2D6-reactive antigens and the sperm’s plasma membrane.
The progressive increase in the proportion of spermatozoa that stain positively with 2D6 McAb/FITC-RAM as they pass through the distal caput and corpus epididymidis indicates uptake of the antigen from the fluid onto the sperm plasma membrane, predominantly onto the tail and to a lesser extent the postacrosomal region. The considerable heterogeneity in the strength of the fluorescence signal on spermatozoa from the distal caput and proximal corpus regions reflects different amounts of 2D6 on the sperm surface. As spermatozoa move into the cauda they become more homogeneous in this respect, although there was significant variation between animals, and it was not uncommon for two peaks of labeled cells to be present. Given the high viscosity of rat epididymal luminal fluid, it is not unexpected that efficient mixing of spermatozoa with newly secreted protein would be time dependent and facilitated by peristaltic contractions of the smooth muscle surrounding the duct. buy zyrtec online