What is :-Hypo-osmotic swelling.?

 

These tests determine the sperm membrane structure and function. The presence of large number of vital (living) , but immotile sperms may be indicative of structural defect in flagellum. Hypo-osmotic Swelling Test offers different information about but sperm membrane function is offered by viability test.

 When live spermatozoa are exposed to a solution of low osmolarity 33-80% sperms demonstrate tail swelling. The percentage of sperms, with such curled tails in the treated sample, should be subtracted from the percentage of those that reacted from hypo-osmotic solution.

A normal value is taken as more than 55-60% reacted sperms per sample, and an abnormal value is less than 50% reacted sperms (< 50% coiling). However, this test lacks sufficient critical evaluation to determine its role in evaluation of more detailed  sperm fertilizing capacity.

Basics: This test is based upon the fact that fluid transport occurs across the intact cell membrane under hypo- osmotic conditions until equilibrium is reached between the inside and outside.HOS values may be selectively altered with certain procedures like: Cryopreservation, Presence of sperm antibodies.

 Note: Since some spermatozoa may have curled tails before exposure to hypo-osmotic solution, it is essential to examine the ejaculate before the test. Increase in free radicals, which occur when there is increase in number white blood cells in semen