and HC03in a medium are necessary for inducing the acrosome reaction in ejaculated goat spermatozoa. Washed goat spermatozoa were resuspended in K-1 medium, containing NaC1, KC1, CaC12, MgCl,, NaH2P04, and NaHC03; in K-2 medium, containing NaC1, CaCl,, NaH2P04, and NaHC03; in K-3 medium, containing NaC1, CaCl,, and NaHCO,; and in K-4 medium, containing only NaCl and CaCl,, followed by preincubation in a sealed glass tube at 39.5"C for 1, 2, or 3 h. The sperm acrosome reaction was evaluated by the trypan blue-Giemsa method and hamster test. The results were essentially the same in all cases. Following preincubation for 1 h, however, the percentage of acrosome-reacted spermatozoa, the proportion of zona-free hamster eggs penetrated by spermatozoa, and the average number of spermatozoa in the vitellus of these penetrated eggs were low; all values indicated a significant increase with preincubation for 2 and 3 h. The presence of K' , Mg2 + , PO4&, and HCOs-in the medium thus does not appear necessary for inducing the acrosome reaction in goat spermatozoa, since they can undergo the reaction during preincubation in a simple physiological salt solution containing only NaCl and CaC12 when preincubated in sealed glass tubes at 39.5"C.
The present study was carried out to determine whether K', MgZ+, Capacitation and the subsequent acrosome reaction in spermatozoa are prerequisites for mammalian fertilization (see Bedford, '70). It is established that these events can be induced not only in the female reproductive tract at estrus, but also in a chemically defined medium (see Bedford, '70). The medium used for inducing capacitation and/or the acrosome reaction contains Na+ , K + , Ca2 + , and Mg2 +