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Sperm Function Test

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Toxicity arising from excess exposure to oxygen (O2) is an inherent challenge to aerobic life. The harmful effects of O2 are attributed to its reduced form (superoxide radical: O2-) or its by-products combined with other highly unstable molecules (hydrogen peroxide: H2O2; hydroxyl radical: HO-). These substances, called oxygen free radicals (from English Reactive Oxygen Species; ROS) have harmful effects in cascade with the surrounding cells in an almost instantaneous way. Cell survival in the face of free radical attack depends, therefore, on the balance between the processes of production and elimination of ROS.


Any circumstance that unbalances these two processes can induce the installation of a condition called oxidative stress, in which the formation of free radicals (oxidizing agents) to antioxidants prevails.


Although the in vivo acrosomal reaction involves a series of complex physiological events, it can also be determined in vitro, that is, in the laboratory.

The acrosomal reaction test evaluates the sperm fecundity potential and the result is expressed in:

  • Percentage of spermatozoa with intact acrosome;

  • Percentage of sperm with damaged acrosome.

Fluorescent markers are used that bind to the sperm acrosome, allowing visualization of the region under a fluorescence microscope. This test should be performed on men with a history of infertility or who are planning or having failed attempts at in vitro fertilization.

Out of normality results indicate that spermatozoa are releasing their digestive enzymes prematurely, making them unable to penetrate the layers of cells that surround the oocyte, compromising the sperm's fertile potential, resulting in infertility.


intact acrosome


acrosome released




The acrosome is the region of the head of the sperm that is membrane-coated and composed of enzymes. These enzymes have the biological function of breaking down the cell layers that surround the oocyte (Cumulus oophorus and zona pellucida), thus allowing sperm penetration and fertilization. The release of these enzymes is called an acrosome reaction.

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  • Liu et al. The proportion of human sperm with poor morphology but normal intact acrosomes detected with pisum sativum agglutinin correlates with in vitro fertilization. Fertil Steril 1988, p. 288-293.

  • Christopher DJ. Biological basis for human capacitation-revisited. H Play Update 2017; 23(3): 289–299.

  • Ranéa C et al. Sperm motility quality in asthenozoospermic samples during prolonged in vitro incubation under anaerobic conditions. Andrology (Suppl): 90-90.

  • Paris and Hallak. Effects of caffeine supplementation in post-thaw human semen over different incubation periods. Andrology 2016; 48(9):961-966.

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