title: Longitudinal and radial gradients of PO(2) in the hamster cheek pouch microcirculation.
abstract: OBJECTIVE
  The aim of this study was to determine longitudinal and radial gradients in oxygen tension (PO(2)) in microvessels of the hamster cheek pouch.
  
  
  METHODS
  We measured PO(2) using the phosphorescence-quenching method in two orders of arterioles (45.8 +/- 5.5 and 19.9 +/- 1.8 micro m diameter), capillaries, and two orders of venules (50.5 +/- 3.4 and 21.4 +/- 2.0 micro m diameter) in order to determine the longitudinal PO(2) gradient. At the arteriolar and venular sites, we also measured PO(2) at four different sites for an analysis of radial PO(2) gradients: centerline, inside wall (larger arteriole and venule only), outside wall, and interstitium. We used 10 hamsters weighing 115 +/- 27 g anesthetized with pentobarbital intraperitoneally and maintained with alpha-chloralose intravenously. The cheek pouch was everted and a single-layered preparation was studied by intravital microscopy. Albumin-bound Pd-porphyrin was infused into the circulation and excited by flash illumination at 10 Hz, with a rectangular diaphragm limiting the excitation field to 5 x 25 micro m.
  
  
  RESULTS
  In the longitudinal direction, intravascular PO(2) decreased significantly (P < 0.01) from large arterioles (39.5 +/- 2.3 mmHg) to small arterioles (32.2 +/- 0.3 mmHg), then to capillaries (30.2 +/- 1.8 mmHg), and on to small venules (27.3 +/- 2.1 mmHg) and large venules (25.5 +/- 2.2 mmHg). In the radial direction, PO(2) decreased significantly (P < 0.01) in and around larger arterioles, and to a lesser extent, around the smaller ones (P < 0.05). There was no significant PO(2) gradient, longitudinal or radial, associated with venules. The PO(2) difference from the centerline to the outside wall in large arterioles was 8.3 +/- 1.4 mmHg, and most of the decline in PO(2) in the radial direction was contributed by the intravascular difference (4.7 +/- 2.1 mmHg) and only about 1.0 +/- 2.7 mmHg by the transmural difference.
  
  
  CONCLUSIONS
  Our data show that there are large intra-arteriolar radial PO(2) gradients, but no large transmural PO(2) differences, suggesting that the oxygen consumption of the microvessel wall is not exceptionally high.
authors.affiliation: Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, Brazil.
authors.forename: Helena
authors.initials: H
authors.lastname: Carvalho
authors.forename: Roland N
authors.initials: RN
authors.lastname: Pittman
mesh_terms: D000818:Animals; D001160:Arterioles / Q000502:physiology; D002196:Capillaries / Q000502:physiology; D002610:Cheek / Q000098:blood supply / Q000502:physiology; D006224:Cricetinae; D004058:Diffusion; D008163:Luminescent Measurements; D008297:Male; D008647:Mesocricetus; D008833:Microcirculation / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D012867:Skin / Q000098:blood supply* / Q000378:metabolism; D014699:Venules / Q000502:physiology
chemical_list: D010100:Oxygen