Thèse soutenue

Contribution à l'étude des mécanismes de régulation du volume des hépatocytes isolés de turbot (Scophthalmus maximus) en condition hypo-osmotique : principaux effecteurs et voies de signalisation intracellulaire
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Auteur / Autrice : Hélène Ollivier
Direction : Guy Nonnotte
Type : Thèse de doctorat
Discipline(s) : Physiologie
Date : Soutenance en 2005
Etablissement(s) : Brest

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Résumé

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When turbot hepatocytes are exposed to a reduction of extracellular osmolality, they swell by about 20 % within first minutes after the hyposmotic shock. Cells subsequently undergo a RVD (Regulatory Volume Decrease) process to recover their original volume. This volume regulation process require coordinated mechanisms to sense volume perturbations, amplify and transduce the signal to the RVD effectors. Cell volume is regulated by the loss of K+ and Cl- with osmotically obligated water by activation of separate K+ and Cl- channels as well as K+/Cl- co-transporter and Cl/HCO3- exchanger. Signaling pathways involve many kinases ( PTK, PI3K, PKC, p38MAPK). . . ), phospholipases A2, C and D, arachinodic acid and eicosanoids and calcium, whose concentration strongly increases after hyposmotic stimulation. Cytoskeletal proteins also contribute to RVD process. Moreover, ATP released in extracellular medium by action of a CFTR-type channel or exocytosis is an important second messenger which acts as an auto/paracrine factor via purinergic receptors activation. The aim of this study was to determine the main cellular events linked to turbot hepatocytes RVD process and to attempt to replace them in the context of a complex and integrative response.