title: Red cell flux during the cardiac cycle in the rabbit myocardial microcirculation.
abstract: OBJECTIVE
  (1) To measure regional phasic myocardial red cell flux during a cardiac cycle using a laser Doppler velocimeter. (2) To test the responses of regional red cell flux to a vasodilator (adenosine), a vasoconstrictor (angiotensin II), and an inotrope (isoproterenol).
  
  
  METHODS
  Using an anaesthetised open-chest rabbit with the pericardium intact a 140-micron-tip fibre optic probe was placed in the left ventricular myocardium in various locations. With the fibre in place drugs were given to alter myocardial loading conditions while red cell flux was registered.
  
  
  RESULTS
  Phasic red cell flux was similar in the epicardium to endocardium giving an average endo/epi ratio of 1.14 in the rabbit heart. At least two peaks of increased red cell flux within a single cardiac cycle were observed. Some unique patterns for red cell flux were observed in specialised myocardial structures. Adenosine increased red cell flux but minimally changed the pattern of phasic flux throughout the cycle.
  
  
  CONCLUSIONS
  Laser Doppler velocimetry permits the recording of phasic red cell flux during the cardiac cycle in the myocardial microcirculation. Its pattern is determined by both coronary arterial inflow and venous outflow. The pattern of red cell flux may be characteristic for a region-probably determined by difference in tissue pressure (attributable to the pattern of muscle fibre shortening and collagen tethering) and changes in capillary length and density.
authors.affiliation: Department of Medicine, Queen Elizabeth II Health Sciences Centre, New Halifax Infirmary, N.S., Canada.
authors.forename: G A
authors.initials: GA
authors.lastname: Klassen
authors.forename: K D
authors.initials: KD
authors.lastname: Barclay
authors.forename: R
authors.initials: R
authors.lastname: Wong
authors.forename: B
authors.initials: B
authors.lastname: Paton
authors.forename: A Y
authors.initials: AY
authors.lastname: Wong
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003971:Diastole; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D007545:Isoproterenol / Q000494:pharmacology; D017078:Laser-Doppler Flowmetry; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D013599:Systole; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000804:Angiotensin II; D000241:Adenosine; D007545:Isoproterenol