Characteristics of motor apparatus in testicular, epididymal and ejaculated spermatozoa: A study using demembranated sperm models

Abstract

Hamster spermatozoa taken from the testis and caput epididymidis are virtually immotile, while cauda epididymal and ejaculated spermatozoa are capable of active progressive movement. Capacitated and ‘activated’ spermatozoa have very vigorous motility characterized by whiplash-like beating of their flagella. When spermatozoa of these five types were demembranated with Triton X-100 and exposed to ATP (and cAMP), all of them began active movement, suggesting that the motor apparatus has already been functionally assembled even before the spermatozoa leave the testis. However, the percentage of spermatozoa activated and the pattern and intensity of activation were somewhat different among these types of spermatozoa. Mature (cauda epididymal and ejaculated) spermatozoa were activated best followed by the caput epididymal spermatozoa. The testicular spermatozoa were least activated. This suggests that the motor apparatus in the spermatozoon ‘matures’ or its characteristics change during epididymal transit. Upon exposure to ATP (and cAMP) demembranated cauda epididymal (hamster and guinea pig) and ejaculated (hamster and human) spermatozoa began vigorous whiplash-like movement. The movement was very similar to or identical with the ‘activated’ movement that membrane-intact capacitated spermatozoa display about the time of fertilization. It is unlikely that the characteristics of the sperm motor apparatus changes during capacitation. The motor apparatus in fresh epididymal and ejaculated spermatozoa must be merely prevented by some mechanisms from effecting the ‘activated’ type of flagellar movement.