Heparin-glutathione III: study with fluorescent probes as indicators of membrane status of bull sperm

Sperm obtained from bull epididymes were used to validate in vitro the effect of heparin and reduced glutathione on sperm membrane status, with the use of sodium dodecyl sulfate (SDS) and Triton X-100 in the presence of propidium iodide (IP) and diacetate fluorescein (FDA). The metabolic activities of treated sperm were qualitatively monitored using an alamar Blue Redox fluorescence indicator. Heparin did not damage the sperm plasma membrane, whereas GSH and SDS at 26 h of incubation dissolved the plasma membrane and the acrosome. On the other hand, at time zero, Triton X-100 showed 75% of sperm stained with IP, indicating plasma membrane damage. Results validated by electron microscopy of thin sections of treated sperm showed complete lack of the membrane, acrosome, and postacrosomal membrane system with 0.01% Triton X-100. Extracellular 15 mM GSH completely disappeared the plasma membrane over the sperm nucleus, leaving the postacrosomal membrane system and nucleus without apparent damage. The metabolic activity was supported over 52 h of incubation in any of the incubation systems tested, including Triton X-100, which showed a spermaticide effect. The authors propose that membrane damage does not mean they are dead, no matter the vital stain employed, and also that FDA-IP staining can be used as a fluorescent marker of sperm plasmatic membrane permeabilization and nuclear swelling.