Changes in Actin Distribution of Ram Spermatozoa under Different Experimental Conditions

Abstract

The purpose of this study was to determine the presence of actin in ejaculated ram spermatozoa and the changes of localization that actin undergoes as a consequence of certain in vitro-induced physiological states. Using indirect immunofluorescence (IIF), three different patterns of staining (defined immunotypes) were established in ejaculated sperm. The three sperm immunotypes showed actin labelling in flagellum, neck and post-acrosomal area, differing on the labelling in the acrosomal region that was complete in immunotype 1, partial (frequently concentrated in the apical area, punctuate form) in immunotype 2, and totally absent in immunotype 3. The main subpopulation in ejaculate was immunotype 1 that represented 68% of total sperm, while 21% corresponded to immunotype 2 and only 10% corresponded to immunotype 3. Selection of high-quality sperm using a dextran/swim-up procedure hardly influenced the proportion of each immunotype resulting in a slight increase in type 1 sperm. Cold-shock treatment and in vitro capacitation induced a partial loss of actin labelling in the acrosomal area, whereas the ionophore-induced acrosomal exocytosis provoked a total loss of the acrosomal actin labelling, a phenomenon partially inhibited by phalloidin.