title: No effect of menstrual cycle on LDL oxidizability and particle size.
abstract: OBJECTIVE
  Premenopausal women have a lower incidence of cardiovascular disease than men, but this female advantage disappears after menopause, suggesting that female sex hormones exert some cardioprotective effects. One of the mechanisms proposed to explain this cardioprotection is the antioxidant properties of estrogens. The aim of this work was to assess whether fluctuations in ovarian hormones, particularly 17beta-estradiol (E(2)), during the menstrual cycle were associated with changes in the low-density lipoprotein (LDL) particle size, fatty acyl composition, alpha-tocopherol content and in vitro oxidizability.
  
  
  METHODS
  Twenty-eight healthy premenopausal women (mean age: 32.2 years) participated in the study. Blood was drawn on days 3 (menstrual phase), 14 (follicular phase) and 22 (luteal phase) of the menstrual cycle for plasma determinations and LDL isolation. Plasma E(2), progesterone, follicle-stimulating hormone and luteinizing hormone were determined by immunoassay. LDL oxidation by Cu(2+)- and 2,2'-azobis (2-amidinopropane) was measured by the formation of conjugated dienes, LDL particle size by quasi-elastic light scattering, fatty acyl composition by gas chromatography, alpha-tocopherol by reversed phase HPLC. A within-subjects analysis of variance was performed to determine significant differences of the variables over the course of a subject's menstrual cycle.
  
  
  RESULTS
  The LDL oxidizability indices (lag time before the onset of propagation and the maximal oxidation rate) did not change during the menstrual cycle. The LDL particle size (24.8+/-1.7 nm diameter), alpha-tocopherol (11.7+/-3.7 nmol/mg LDL protein) and fatty acyl composition also remained constant.
  
  
  CONCLUSIONS
  The LDL physicochemical properties and oxidizability are not affected by menstrual cycle phase.
authors.affiliation: Department of Physiology, Medicine School, University of the Basque Country, 48080 Bilbao, Spain.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: Ruiz-Sanz
authors.forename: Rosaura
authors.initials: R
authors.lastname: Navarro
authors.forename: Rosa
authors.initials: R
authors.lastname: Martínez
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Hernández
authors.forename: Roberto
authors.initials: R
authors.lastname: Matorras
authors.forename: M Begoña
authors.initials: MB
authors.lastname: Ruiz-Larrea
mesh_terms: D000328:Adult; D000578:Amidines; D008078:Cholesterol, LDL / Q000097:blood / Q000378:metabolism*; D003300:Copper; D004958:Estradiol / Q000097:blood / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000097:blood / Q000378:metabolism*; D010084:Oxidation-Reduction; D010316:Particle Size; D017697:Premenopause; D011374:Progesterone / Q000097:blood; D024502:alpha-Tocopherol / Q000097:blood
chemical_list: D000578:Amidines; D008078:Cholesterol, LDL; D011374:Progesterone; D004958:Estradiol; C046728:2,2'-azobis(2-amidinopropane); D003300:Copper; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; C028419:cuprous chloride; D024502:alpha-Tocopherol