title: Functional characterization of isolated, perfused outermedullary descending human vasa recta.
abstract: OBJECTIVE
  The renal medulla plays an important role in the control of water and salt balance by the kidney. Outer medullary descending vasa recta (OMDVR) are microscopic vessels providing blood flow to the renal medulla. Data on the physiology of human vasa recta are scarce. Therefore, we established an experimental model of human single isolated, perfused OMDVR and characterized their vasoactivity in response to angiotensin II and to pressure changes.
  
  
  METHODS
  Human non-malignant renal tissue was obtained from patients undergoing nephrectomy due to renal cell carcinoma. OMDVR were dissected under magnification and perfused using concentric microscopic pipettes. The response of OMDVR to angiotensin II and pressure changes was quantified in serial pictures. All patients signed a consent form prior to surgery.
  
  
  RESULTS
  Outer medullary descending vasa recta constricted significantly after bolus applications of angiotensin II. OMDVR constriction to angiotensin II was also concentration dependent. Response to luminal pressure changes was different according to the diameter of vessels, with larger OMDVR constricting after pressure increase, while smaller ones did not.
  
  
  CONCLUSIONS
  Outer medullary descending vasa recta constrict in response to angiotensin II and pressure increases. Our results show that OMDVR may take part in the regulation of medullary blood flow in humans. Our model may be suitable for investigating disturbances of renal medullary circulation in human subjects.
authors: Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, Berlin, Germany. mauricio.sendeski@charite.de
authors: M M
authors: MM
authors: Sendeski
authors: Z Z
authors: ZZ
authors: Liu
authors: A
authors: A
authors: Perlewitz
authors: J F
authors: JF
authors: Busch
authors: O
authors: O
authors: Ikromov
authors: S
authors: S
authors: Weikert
authors: P B
authors: PB
authors: Persson
authors: A
authors: A
authors: Patzak
mesh_terms: D000368:Aged; D000804:Angiotensin II / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D004210:Dissection; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007679:Kidney Medulla / Q000098:blood supply* / Q000601:surgery; D008297:Male; D040542:Mechanotransduction, Cellular; D055806:Microvessels / Q000187:drug effects* / Q000601:surgery; D012079:Renal Circulation / Q000187:drug effects*; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D000804:Angiotensin II