Biology of the Scrotum. I. Temperature and Androgen as Determinants of the Sperm Storage Capacity of the Rat Cauda Epididymidis

The lower temperature of the scrotum is a major determinant of the sperm storage capacity of the rat cauda epididymidis. Abdominal temperature significantly reduced sperm numbers in the rat cauda at 2 days and further to 20-25% of the controls by 16 days, despite continuous replacement of spermatozoa from a normal scrotal testis. Ipsilateral castration, when spermatozoa are not replaced, made even more obvious the immediate suppressive effect of body temperature on the storage capacity of the cauda. Furthermore, chronic exposure of the pre- and postpubertal epididymis to body temperature throughout the final growth period severely limited development of the storage potential of the cauda to about one-fifth of that reached in the scrotum. Histological sections indicate this reduction is due to a diminution in the diameter and possibly also length of the duct. Though temperature appears relatively the more influential, the retention of spermatozoa in a viable state of the cauda is compromised also by androgen withdrawal. Together, however, the low temperature of the scrotal location and testicular androgen act in a synergistic manner to optimize the storage capacity of the cauda epididymidis, as well as the viability of the spermatozoa there. Ligation experiments indicate that the rapid disappearance of spermatozoa following androgen withdrawal or imposition of body temperature results from their accelerated passage into the vas deferens and beyond.