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Updated: May 18, 2026

Fluorimetric Techniques for the Assessment of Sperm Membranes
Published on: November 28, 2018
The hypo-osmotic swelling test for evaluation of sperm membrane integrity
Sivakumar Ramu1, Rajasingam S Jeyendran
1Andrology Laboratory Services Inc, Chicago, IL, USA.
Abstract:
A functional membrane is requisite for the fertilizing ability of spermatozoa, as it plays an integral role in sperm capacitation, acrosome reaction, and binding of the spermatozoon to the egg surface. The hypo-osmotic swelling (HOS) test evaluates the functional integrity of the sperm's plasma membrane and also serves as a useful indicator of fertility potential of sperm. The HOS test predicts membrane integrity by determining the ability of the sperm membrane to maintain equilibrium between the sperm cell and its environment. Influx of the fluid due to hypo-osmotic stress causes the sperm tail to coil and balloon or "swell." A higher percentage of swollen sperm indicates the presence of sperm having a functional and intact plasma membrane. Here, we present the detailed protocol for performing the HOS test and explain the results for interpretation.
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