Developmental Changes Occurring in the Lipids of Ram Epididymal Spermatozoa Plasma Membrane 1

Abstract

Ram spermatozoa were obtained from different regions (caput, corpus, and cauda) of the epididymis and their plasma membrane was removed using a nitrogen cavitation treatment (750 psi, 10 min equilibration at 4 degrees C). Membrane was recovered after sucrose gradient centrifugation and identified using 125I-succinylated concanavalin A (125I-succConA) as a surface marker. Based on fluorescein isothiocyanate-succConA (FITC-succConA) labeling and electron microscopy, cavitation removed plasma membrane from the anterior sperm head in the area overlying the acrosome. Cholesterol was the major sterol in plasma membrane, with desmosterol present in sperm entering the epididymis (caput sperm) but negligible in sperm after epididymal transit (cauda sperm). Ethanolamine and choline phosphoglycerides represented 70-80% of membrane phospholipids, with the ethanolamine fraction decreasing relative to choline phosphoglycerides during epididymal transit. The molar ratio of cholesterol to phospholipid increased in the plasma membrane during maturation. The bulk phospholipid-bound fatty acids consisted primarily of palmitoyl acyl groups (16:0) in caput sperm and docosahexaenoyl acyl groups (22:6) in cauda sperm. The choline phosphoglyceride fraction was purified and analyzed. It consisted of a mixture of ether acyl glycero-3-phosphocholine and diacyl phosphoglyceride, with the dominant acyl residue, at all stages of epididymal maturation, being 22:6 throughout epididymal transit. The significance of these findings relative to acquisition of fertilization capacity by sperm during epididymal maturation is discussed.

Plasma membrane of trout spermatozoa: I. Isolation and partial characterization

“…This method overcomes the problems associated with the use of detergent, mechanical homogenization, hypotonic shock or sonication (McNamee 1989). The" yield of membrane protein following release of the plasma membrane by nitrogen cavitation was always equal or greater than 1% of the total cell protein (Gillis et al 1978:1%;Mack et al 1986: 1.6%), i.e., according to Gillis et al (1978) and Parks and Hammerstedt (1985) 20 to 30% of the membrane protein was obtained by this procedure.…”

Co‐expression and interaction of cubilin and megalin in the adult male rat reproductive system

“…In fact, there is a 54% decrease in the total membrane phospholipid content from caput to corpus epididymidis (Aveldano et al, 1992). While an phospholipids show a decrease, those found predominantly in the inner leaflet (phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol and ethanolamine plasmalogen) show a much greater decrease than those found predominantly on the outer leaflet (phosphatidylcholine, choline plasmalogen and sphingomyelin) which remain relatively stable (Aveldano et al, 1992;Parks and Hammerstedt, 1985). The result ofthis is that the sperm plasma membrane, which already contains an unusually high proportion of polyunsaturated phospholipids from the outset, acquires and even greater degree of unsaturation as the sperm matures.…”

Remodelling of Lipid Rafts during In vitro Capacitation and Acrosome Reaction of Ram Spermatozoa

“…The cholesterol: phospholipid ratio (0.38) is considerably lower than that in other mammalian species [13], which could be the reason why albumin-mediated cholesterol efflux might not be necessary during ram sperm capacitation [14,15]. This special low content in cholesterol might also be related to the increased time required for ram sperm capacitation [16], and the high sensitivity to cryodamage [17,18].…”