Effect of Aging on the Fertilizing Capacity of Testicular Spermatozoa from the Rabbit1

Attempts were made to induce the fertilizing capacity of testicular spermatozoa from rabbits. Aging in vitro was ruled out because the fertilizing capacity of mature spermatozoa decreased to less than 2% when stored for 48 h at room temperature and 1.5 × 106 were inseminated. This occurred whether the spermatozoa were diluted or undiluted, and was not improved by addition of catalase, theophylline or myo-inositol to the incubation medium. Testicular spermatozoa were unable to fertilize ova after retention in the rete testis from four to six days or after retention in a sperm-free distal cauda epididymidis for two, three or four days. However, the fertilizing capacity of mature spermatozoa retained in the distal cauda under the same conditions fell from 57 percent to 17 percent over a two to four day period. The inability of testicular spermatozoa to acquire the capacity to fertilize ova under these conditions is discussed.