Structural and functional responses of extremity veins to long-term gravitational loading or unloading-lessons from animal systems

Emil Monos, Gábor Raffai, Gabriella Dörnyei, György L. Nádasy, Erzsébet Fehér

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13 Citations (Scopus)


Long, transparent tubular tilt-cages were developed to maintain experimental rats either in 45{ring operator} head-up (orthostasis model), or in 45{ring operator} head-down body position (antiorthostasis model) for several weeks. In order to study the functional and structural changes in extremity blood vessels, also novel pressure angiograph systems, as well as special quantitative electron microscopic methods were applied. It was found that several adaptive mechanisms are activated in the lower limb superficial veins and microvessels of muscles when an organism is exposed to long-term (1-2 weeks) orthostatic-type gravitational load including a reversible amplification of the pressure-dependent myogenic response, tuning of the myogenic tone by Ca++- and voltage-sensitive K+ channels in humans, augmentation of the intramural sympathetic innervation involving an increased nerve terminal density and synaptic vesicle count with functional remodeling, reorganization of vascular network properties (microvascular rarefaction in muscles, decreased branching angles in superficial veins), and responses of an endothelin and platelet-derived growth factor (PDGF) containing vesicle system in the endothelium. On the other hand, when applying long-term head-down tilting, the effects are dichotomous, e.g. it suppresses significantly the pressure-induced myogenic response, however does not diminish the adventitial sympathetic innervation density.

Original languageEnglish
Pages (from-to)406-414
Number of pages9
JournalActa Astronautica
Issue number4-7 SPEC. ISS.
Publication statusPublished - Feb 1 2007



  • Antiorthostasis
  • Endothelium
  • Orthostasis
  • Vascular adaptation
  • Vascular innervation
  • Venous tone

ASJC Scopus subject areas

  • Aerospace Engineering

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