title: The effect of hormone replacement therapy on Ca2+ mobilization and P-selectin (CD62P) expression in platelets examined under flow cytometry.
abstract: A series of events, such as increase of cytoplasmic free calcium (Ca2+) and expression of P-selectin (CD62P), an adhesion molecule, on the platelet surface, are significant indicators of platelet activation. We have used flow cytometry to examine Ca2+ mobilization and CD62P expression in platelets in whole blood obtained in women prior to, and after, different forms of hormone replacement therapy. Thirty-two women completed a protocol consisting of two consecutive 1-month periods under oestradiol (E2), administered orally (2 mg/day) or transdermally (50 microg/day) in random order, followed by a 4-week transdermal sequential regime, in which, during the last 14 days, either progesterone (300 mg/day) or medroxyprogesterone acetate (5 mg/day) was added to the 50 microg/day E2, administered orally in random order. None of the hormonal combinations determined significant changes in Ca2+ mobilization or CD62P expression in non-stimulated platelets. However, stimulation of platelets with adenosine diphosphate, but not with thrombin, caused a significant increase in cytoplasmic Ca2+ concentration during treatment with transdermal E2 plus progesterone. Also when stimulating with thrombin, transdermal E2 was more active than oral E2 in increasing CD62P expression, a difference that was not reduced by the addition of progestogens. In conclusion, hormone replacement therapy only increased Ca2+ mobilization or CD62P expression in stimulated platelets, and then followed a varied pattern that was dependent on the stimulant and on the specific hormonal formulation.
authors.affiliation: Department of Pediatrics, Obstetrics and Gynecology, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.
authors.forename: Maria Cinta
authors.initials: MC
authors.lastname: García-Martínez
authors.forename: Manuel
authors.initials: M
authors.lastname: Labiós
authors.forename: Carlos
authors.initials: C
authors.lastname: Hermenegildo
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Tarín
authors.forename: Enrique
authors.initials: E
authors.lastname: O'Connor
authors.forename: Antonio
authors.initials: A
authors.lastname: Cano
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004958:Estradiol / Q000627:therapeutic use*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D020249:Hormone Replacement Therapy; D006801:Humans; D008593:Menopause / Q000187:drug effects / Q000378:metabolism*; D008875:Middle Aged; D019007:P-Selectin / Q000096:biosynthesis*; D015539:Platelet Activation / Q000187:drug effects
chemical_list: D019007:P-Selectin; D004958:Estradiol; D002118:Calcium