Jeyendran et al developed the hypoosmotic swelling test to evaluate human sperm. The tails of normal sperm will swell if exposed to a hypoosmotic solution.
Specimen rejection: > 5% tail swelling in untreated sperm
Hypoosmotic solution: 50:50 mixture of 150 mosmol fructose and 150 mosmol sodium citrate (calculated ionic strength 0.15). The solution consists of 7.35 grams sodium citrate•2 H2O and 13.51 grams fructose dissolved in 1,000 mL of distilled water.
Method:
(1) 0.1 mL of fresh ejaculate is mixed with 1.0 mL of the hypoosmotic solution
(2) The mixture is incubated at 37°C for >= 30 minutes.
(3) A sample is examined in a counting chamber under phase contrast.
Tail swelling may be:
(1) focal at the tip
(2) involve the distal half
(3) involve the entire length with a slight increase in diameter
(4) saccular change along the entire length
percent of spermatozoa with tail swelling =
= (number of spermatozoa with tail swelling) / (total number of spermatozoa counted) * 100%
Interpretation:
• Normal sperm showed 60.1% +/- 12.5% sperm with swollen tails.
• A low percent of sperm with swollen tails correlates with reduced oocyte penetration and reduced sperm motility. This may correlate with reduced male fertility.
