The Effect of Cholesterol on Spermatozoa Membranes: Investigation Using Spin Probes

Cholesterol plays an important role in the structural organization and functioning of sperm membranes. The purpose of this work was to study the structural changes of human sperm membranes using spin probes after removing cholesterol from them with the help of methyl-β-cyclodextrin, which binds cholesterol. Using a model system (liposomes with different cholesterol content), it was shown that the presence of cholesterol in liposomes affects the EPR spectra of the spin probe of 5-doxyl-stearic acid dissolved in the lipid bilayer, causing an increase in the microviscosity of the membrane. The extraction of cholesterol from sperm membranes by spermatozoa treatment with methyl-β-cyclodextrines caused changes in the EPR spectra of 5-doxyl-stearic acid dissolved in sperm membranes, demonstrating the membrane fluidization.