The fine structure and the biosynthesis of cholesterol were studied in the epididymis and ductus deferens of the following groups (24–30 animals per group) of mice: intact, castrated for 30 or 60 days, and castrated animals receiving testosterone.

The most distinctive features of cells along the ductus deferens is the whorled configuration of smooth endoplasmic reticulum, which is in contrast to the tubular reticulum found in the caput, corpus, and cauda epididymidis. It is shown that cells from all segments of the tract incorporate [1-¹⁴C]-acetate into cholesterol. Although the caput epididymidis incorporates significantly more acetate than other segments after 1-hour incubation, at the end of 3-hours incubation more acetate has been incorporated into cholesterol in the vas deferens than in the other segments. The effects of castration and hormone replacement therapy are detailed, and the findings are discussed in respect to smooth membrane involvement in sterol biosynthesis and the possible differences in function between the tubular and whorled configurations of reticulum. The effect that the ability of the epididymis to synthesize sterols might have on spermatozoa in the lumen of the ducts is discussed.