Prolonged storage of human spermatozoa at room temperature or in a refrigerator

Spermatozoa from patients who underwent in vitro fertilization (IVF) therapy were prepared free from seminal plasma with the use of IVF culture medium supplemented with 8% human serum. Samples were then stored either at room temperature or in a refrigerator, and their motility and ability to penetrate zona-free hamster eggs were assessed every second day. With storage at room temperature, motility declined by less than half over the first 14 days, with some samples still active 20 days after preparation. The ability of the samples to penetrate hamster eggs was unchanged during the first 6 days of storage, and most of the samples still had positive tests after 14 days. Some spermatozoa could still penetrate after 17 days. Room-temperature-stored spermatozoa were still able to fertilize human oocytes 5 days after preparation. With storage in a refrigerator motility declined rapidly, and few sperm were motile after 14 days. However, these samples penetrated relatively more hamster eggs after 14 days' storage than room-temperature-stored samples did. Spermatozoa stored overnight in a refrigerator had significantly higher hamster egg penetration rates than spermatozoa stored overnight at room temperature. After storage overnight at room temperature, false-positive and false-negative results of hamster egg penetration tests were common in relation to IVF outcome; after refrigerated storage, no false-negative results were found.