Isolation and unique composition of purified head plasma membrane from rooster sperm

Abstract

The structure, composition, and function of membranes from organelles of mammalian spermatozoa differ from each other and from the sperm's plasma membrane. Avian sperm studies have suffered from the lack of a technique to isolate these various membranes, which the current study now provides. Nitrogen cavitation and differential centrifugation separated head plasma membranes (HPM) of rooster sperm from sperm debris, acrosomal membranes, and mitochondrial membranes and characterized these membranes enzymatically and microscopically. The HPM was enriched in acid phosphatase (marker enzyme for HPM; 1,814.81 +/− 470.43 micromol phosphate released/microg protein vs. 868.53 +/− 75.55 for whole semen; a 202.5 +/− 37.8% enrichment, mean +/− SE, P < 0.001), with less (P < 0.001) mitochondrial and acrosomal enzyme activity. The mitochondrial fraction had 515.1 +/− 167.6% more succinate dehydrogenase activity (marker for mitochondria, P < 0.001) and the acrosomal fraction had 315.4 +/− 61.2% more acetylglucosaminidase activity (marker for acrosome, P < 0.0001) than whole semen. Thin layer and gas chromatography showed that HPM lipids had more (P < 0.05) sphingomyelin and phosphatidylserine, and less phosphatidylcholine and phosphatidylethanolamine than did the sperm body membranes (SBM). Overall, HPM had less polyunsaturated fatty acids than SBM (36.8 +/− 3.4 vs. 44.5 +/− 1.7% of total phospholipids, P < 0.05). HPM had slightly more n3 (3.2 +/− 0.5 vs. 1.3 +/− 0.2%, P < 0.01) but much less n6 (33.6 +/− 3.3 vs. 43.3 +/− 1.9%, P < 0.01), specifically less C22:4n6. Future study of avian sperm will be able to reliably characterize the structure-function relationships of specific sperm membranes.