The lipid composition of hamster epididymal spermatozoa was examined.
Caput epididymal spermatozoa were isolated by Percoll density gradient
centrifugation without contamination by other cells and they had a sp
ecific gravity of 1.10-1.12 g cm(-3). Caput and cauda epididymal sperm
atozoa showed little difference in the amounts of total fatty acid and
total sterol. However, sterol composition changed markedly during the
transit of spermatozoa through the epididymis: the amount of choleste
rol decreased, while the amount of desmosterol and cholesta-7,24-dien-
3 beta-ol increased. No significant change in fatty acid composition w
as observed during the transit, although there was a tendency for an i
ncrease in chain length. Both 22:5 and 22:6 represented high percentag
es in fatty acids of hamster spermatozoa. Some difference in lipids wa
s detected between the upper fraction (1.04 g cm(-3)) and the lower fr
action (1.10 g cm(-3)) obtained by the density gradient centrifugation
of cauda epididymal spermatozoa Total fatty acid content of the upper
fraction was IA-fold higher than that of the lower fraction, and the
percentage of 18:0 was lower in the latter fraction with a higher perc
entage of 18:2. The total sterol:total phospholipid ratio in hamster c
auda epididymal spermatozoa was 0.21.