Ether-linked triglycerides of rat epididymis

Abstract

Long-chain n-9 polyunsaturated fatty acids (PUFA), particularly 22:4n-9, are normal components of the plasmenylcholines of rat epididymal spermatozoa. Since these uncommon PUFA are absent from lipids of testicular cells, their accretion is expected to occur during the passage of the gametes through the epididymis. In this work we focused on the neutral lipids that are present in the epididymal caput, corpus, and cauda regions. In addition to cholesteryl esters, the three areas contained ether-linked triglycerides (1-O-alkyl-, and 1-alk-1´enyl- diacylglycerols, ADG). Interestingly, the latter were characterized by high proportions of n9 PUFA. The amounts of these ADG gradually increased during development: they were detected in rat epididymis on day 14 after birth (P14), their amounts increased markedly at P49, in association with the complete differentiation of all epididymal cells, while reaching maximum levels at P55, the time at which the first spermatozoa appeared in the epididymal lumen. In adult rats, the smallest but metabolically most active portion of the epididymis, the corpus, had relatively more 22:4n-9-rich ADG than the other two regions. Our data suggest that epididymal ADG may be involved as lipid intermediates during the active membrane remodeling that spermatozoa are known to undergo during their extra-testicular maturation.