An evaluation of different media for the zona-free hamster egg penetration test.

Hypertonic high-salt Biggers, Whitten, and Whittingham medium was compared with either a complex culture medium (synthetic tubal fluid) or a variant of Tyrode's medium for capacitating donor human spermatozoa to be used in the zona-free hamster egg penetration test. Five sperm preparations showed a slightly higher penetration rate in synthetic tubal fluid than in high-salt Biggers, Whitten, and Whittingham medium, five showed equivalent results, and only two had slightly lower penetration rates. However, in modified Tyrode's medium only one sample showed a lower penetration, while six showed comparable results and five showed higher rates of penetration. This last group included two samples that had demonstrated zero penetration in high-salt Biggers, Whitten, and Whittingham medium. Although no overall significant differences between media in the two series of experiments could be discerned with paired t tests, in view of the lower incidence of false negative results in modified Tyrode's medium and the absence of osmotic stress, this medium may represent a better choice for routine performance of the hamster egg penetration test.