Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables.

OBJECTIVE: To compare the variability of sperm acrosin and hypoosmotic swelling to the more standard semen variables in relationship to controlled periods of sexual abstinence using a defined group of men.
DESIGN: Ten men abstained sequentially for 1, 2, 3, 4, 5, and 10 days and produced an ejaculate after each time period. The ejaculate variables measured at each time point were sperm acrosin, hypoosmotic swelling, volume, sperm number, sperm concentration, sperm motility, sperm morphology, pH, and white blood cells (WBCs). Comparisons were performed between the values obtained at each abstinence period.
RESULTS: The percentage of hypoosmotically reactive spermatozoa did not vary significantly with the abstinence period. Sperm acrosin remained similar up to 5 days of abstinence but decreased almost twofold after 10 days of abstinence. The sperm volume and concentration increased gradually with the length of abstinence, being approximately twofold higher after 10 days of abstinence than after 1 day of abstinence. The total sperm number increased about fourfold from 1 day of abstinence to 10 days of abstinence. The percent normal sperm forms tended to increase until 5 days of abstinence but decreased after 10 days of abstinence. The WBC count showed only a small increase with longer abstinence periods. The pH remained essentially the same.
CONCLUSIONS: The length of abstinence affects the various semen variables differently. An abstinence period of up to 10 days does not alter the hypoosmotic swelling test results. However, the sperm acrosin values decrease after prolonged abstinence so that the abstinence period needs to be taken into consideration when performing this assay.