title: Uridine adenosine tetraphosphate affects contractility of mouse aorta and decreases blood pressure in conscious rats and mice.
abstract: OBJECTIVE
  in the anaesthetized rat, uridine adenosine tetraphosphate (Up(4) A) is a circulating, endothelium-derived vasoconstrictor presumably operating as such in un-anaesthetized animals. The present study investigated the in vivo effects of Up(4) A in conscious mice and rats, and its direct vascular effects in the mouse aorta in vitro.
  
  
  METHODS
  in vivo, Up(4) A was given as step-up infusion at rates of 8-512 nmol min(-1) kg(-1) for 30 min periods in chronically catheterized rodents. In vitro, the effect of Up(4) A on rings of mouse aortae mounted in a myograph was tested.
  
  
  RESULTS
  high doses of Up(4) A (mice: 512 nmol min(-1) kg(-1) ; rats: 128 nmol min(-1) kg(-1) ) caused hypotension (99 (+/-)4 to 64 7(+/-) mmHg and 114 (+/-) 3 to 108 (+/-) 3 mmHg, respectively, both P < 0.01). In rats, Up(4) A significantly decreased sodium excretion by >75% and potassium excretion by approximately 60% without significant changes in urine flow. Exposure of phenylephrine-contracted rings to increasing concentrations of Up(4) A elicited contraction at 10(-7) and 10(-6) molL(-1) (18 ± 2% and 76 (+/-) 16% respectively); unexpectedly, 10(-5) molL(-1) caused a biphasic response with a contraction (19 6(+/-)2%) followed by a relaxation (-46 (+/-) 6%). No relaxation was observed when the concentration was increased further. Bolus exposure to 10(-5) molL(-1) of Up(4) A caused contraction (+80 (+/-) 2%). Added successively to untreated vessels, increasing concentrations of Up(4) A (10(-7) -10(-5) molL(-1) ) induced a biphasic response of contraction followed by relaxation.
  
  
  CONCLUSIONS
  up(4) A has direct biphasic effects on vascular smooth muscle of the mouse aorta but vasoconstriction dominates at low concentrations. In conscious rodents, step-up infusions of Up(4) A elicit hypotension and electrolyte retention.
authors.affiliation: Cardiovascular and Renal Research, Institute of Medical Biology, University of Southern Denmark, Odense, Denmark. pbhansen@health.sdu.dk
authors.forename: P B
authors.initials: PB
authors.lastname: Hansen
authors.forename: A
authors.initials: A
authors.lastname: Hristovska
authors.forename: H
authors.initials: H
authors.lastname: Wolff
authors.forename: P
authors.initials: P
authors.lastname: Vanhoutte
authors.forename: B L
authors.initials: BL
authors.lastname: Jensen
authors.forename: P
authors.initials: P
authors.lastname: Bie
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D003243:Consciousness; D015226:Dinucleoside Phosphates / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D007668:Kidney / Q000502:physiology; D007677:Kidney Function Tests; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D015226:Dinucleoside Phosphates; C529314:uridine adenosine tetraphosphate