The lipids of ram spermatozoa

Abstract

Washed freeze-dried ram spermatozoa were extracted with chloroform-methanol (2:1, v/v) and the crude extracts purified by washing with water and passing through a column of cellulose, the yield of total lipids being 7-9%. Part of this material was hydrolyzed directly, ethanolic KON, methanolic HC1 and aqueous Ba(OH)2 being used as alternative reagents, and part was examined chromatographically with silicic acid (or silica gel) from 2 sources, these being products known to have widely different adsorptive properties. From analytical data on the original lipids and on the various chromatographic fractions it is evident that aldehydrogenic lipids, possibly plasmalogens, are major components (about 55-60%) of the sperm lipids. Choline is the predominating base of these particular compounds, although there are minor amounts of ethanolamine. The behavior towards hydrolytic agents is, however, not that to be expected from the accepted plasmalogens. There is no evidence for the presence of lecithin. Other components of the extracts are free cholesterol (about 8%), hydrocarbons (about 2%), probably sphingomyelin (about 5.5%) and other lipids difficult to characterize, but perhaps including wax esters and glycerides. Despite the purifications employed, non-lipids appeared to be present in appreciable amount, possibly combined with the lipids. Both ethanolic KOH and methanolic HC1 proved inadequate for the complete hydrolysis of some of the lipids. The former sometimes gave "fatty acids" rich in P and "unsaponifiable matter" which became largely water-soluble on refluxing with acetic anhydride. The latter gave a fraction susceptible to further hydrolysis with ethanolic KOH.