title: Membrane fluidity and lipid content of human spermatozoa selected by swim-up method.
abstract: In this work, we examined whether spermatozoa (spz) from normospermic fertile patients and selected by a swim-up (S-U) procedure had a particular membrane fluidity related to their maturity and their lipid content as compared with the sperm cells from the whole ejaculate (total sperm). Swim-up selected sperm had a reduced cytoplasmic space as revealed by a lower creatine kinase (CK) activity compared with total sperm (2 +/- 1 vs. 12 +/- 5 mUI/10(7) spz, p < 0.05). The cholesterol (Chol) and total phospholipid (PL) contents were significantly lower in S-U selected sperm than in total sperm (0.72 +/- 0.08 vs. 1.20 +/- 0.30 nmol/10(6) spz for Chol and 1.77 +/- 0.17 vs. 2.78 +/- 0.50 nmol/10(6) spz for PL, p < 0.05) and such a decrease was observed for the three major membrane PL: phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM). However, these decreases were not associated with a change in either Chol/PL or PC/(PC + PE) molar ratios. Membrane fluidity estimated by fluorescence polarization remained comparable between the S-U sperm fraction and total sperm (fluorescence polarization anisotropy, r, which is inversely proportional to the fluidity: 0.235 +/- 0.006 vs. 0.230 +/- 0.005). The sperm membrane fluidity obtained in normospermic patients was compared with abnormospermic ones (oligoasthenoteratospermia). In abnormospermic patients, the membrane fluidity was decreased in migrated spermatozoa compared with total sperm (anisotropy: 0.210 +/- 0.010 vs. 0.250 +/- 0.013, p < 0.01). Our data suggest that the S-U method selected a subpopulation of mature spermatozoa characterised by a low content of Chol and PL, likely related to a reduced membrane area. The fact that Chol/PL and PC/(PC + PE) molar ratios were unchanged shows a maintenance of the membrane quality. This was confirmed by the fluorescence anisotropy measurement showing no difference in plasma membrane fluidity between S-U selected sperm and total sperm. In abnormal semen the migrated spermatozoa had a lower fluidity compared with total sperm suggesting a defective sperm function. These results bring new elements characterizing the S-U selected spermatozoa.
authors.affiliation: Biologie de la Reproduction, CECOS, Clermont-Ferrand, France. andre.force@u-clermont1.fr
authors.forename: A
authors.initials: A
authors.lastname: Force
authors.forename: G
authors.initials: G
authors.lastname: Grizard
authors.forename: M N
authors.initials: MN
authors.lastname: Giraud
authors.forename: C
authors.initials: C
authors.lastname: Motta
authors.forename: B
authors.initials: B
authors.lastname: Sion
authors.forename: D
authors.initials: D
authors.lastname: Boucher
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003402:Creatine Kinase / Q000378:metabolism; D006801:Humans; D008297:Male; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013094:Spermatozoa / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*
chemical_list: D008563:Membrane Lipids; D003402:Creatine Kinase