Rat testicular dolichols: distribution and accumulation with age.

Dolichols, linear isoprenoids essential in the biosynthesis of N-glycosylated glycoproteins, are abundant in testicular tissue. This study investigated the distribution of dolichols among testicular cell and subcellular fractions. In addition, the accumulation of dolichol within the rat testis as a function of age was investigated. Dolichol content expressed either as total dolichol/testicle or as dolichol/mg protein exhibited a marked and continuous increase between 14 and 60 days of age. The 4-, 6-, 9-, and 12-mo-old animals exhibited only minor increases in testicular dolichol content. Mean value for retired breeders was 279 ng dolichol/mg protein. Although previous studies have suggested that dolichol synthesis occurs primarily within the spermatogenic cell, elutriation-purified spermatogenic cell fractions showed very low concentrations of dolichol. Pachytene spermatocyte and round spermatid fractions contained 25.8 and 36.5 ng dolichol/mg protein, respectively. Washed epididymal sperm also had a very low dolichol content (18.8 ng dolichol/mg protein). Recovery studies during elutriation purification of spermatogenic cells showed that the majority of dolichol was contained within the Sertoli-rich tubular fragments. Microsomal fractions isolated from whole testis exhibited a small enrichment (1.6-fold) in dolichol content, whereas Golgi apparatus fractions exhibited a large (12-fold) enrichment over that of the initial homogenate. These studies suggest that, although dolichols may be synthesized within the spermatogenic cell, they accumulate within the Sertoli cell.