title: Ultraslow myosin molecular motors of placental contractile stem villi in humans.
abstract: Human placental stem villi (PSV) present contractile properties. In vitro mechanics were investigated in 40 human PSV. Contraction of PSV was induced by both KCl exposure (n = 20) and electrical tetanic stimulation (n = 20). Isotonic contractions were registered at several load levels ranging from zero-load up to isometric load. The tension-velocity relationship was found to be hyperbolic. This made it possible to apply the A. Huxley formalism for determining the rate constants for myosin cross-bridge (CB) attachment and detachment, CB single force, catalytic constant, myosin content, and maximum myosin ATPase activity. These molecular characteristics of myosin CBs did not differ under either KCl exposure or tetanus. A comparative approach was established from studies previously published in the literature and driven by mean of a similar method. As compared to that described in mammalian striated muscles, we showed that in human PSV, myosin CB rate constants for attachment and detachment were about 103 times lower whereas myosin ATPase activity was 105 times lower. Up to now, CB kinetics of contractile cells arranged along the long axis of the placental sheath appeared to be the slowest ever observed in any mammalian contractile tissue.
authors.affiliation: Centre de Recherche Clinique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Lecarpentier
authors.affiliation: Department of Pharmaceutical Sciences, University of Antwerp, Wilrijk, Belgium.
authors.forename: Victor
authors.initials: V
authors.lastname: Claes
authors.affiliation: Centre de Recherche Clinique, Centre Hospitalier Régional de Meaux, Meaux, France; INSERM U767, Université Descartes Paris 5, Sorbonne Paris Cité, Paris, France.
authors.forename: Edouard
authors.initials: E
authors.lastname: Lecarpentier
authors.affiliation: Service de Gynécologie-Obstétrique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Guerin
authors.affiliation: Institut de Cardiologie, Hôpital de la Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Hébert
authors.affiliation: Service de Gynécologie-Obstétrique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Arsalane
authors.affiliation: Service de Gynécologie-Obstétrique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Abdelouahab
authors.initials: A
authors.lastname: Moumen
authors.affiliation: Centre de Recherche Clinique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Xénophon
authors.initials: X
authors.lastname: Krokidis
authors.affiliation: Service de Gynécologie-Obstétrique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Francine
authors.initials: F
authors.lastname: Michel
authors.affiliation: Service de Gynécologie-Obstétrique, Centre Hospitalier Régional de Meaux, Meaux, France.
authors.forename: Oumar
authors.initials: O
authors.lastname: Timbely
mesh_terms: D000293:Adolescent; D000328:Adult; D002824:Chorionic Villi / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009218:Myosins / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011247:Pregnancy; D055815:Young Adult
chemical_list: D011189:Potassium Chloride; D009218:Myosins