title: Vascular geometry and oxygen diffusion in the vicinity of artery-vein pairs in the kidney.
abstract: Renal arterial-to-venous (AV) oxygen shunting limits oxygen delivery to renal tissue. To better understand how oxygen in arterial blood can bypass renal tissue, we quantified the radial geometry of AV pairs and how it differs according to arterial diameter and anatomic location. We then estimated diffusion of oxygen in the vicinity of arteries of typical geometry using a computational model. The kidneys of six rats were perfusion fixed, and the vasculature was filled with silicone rubber (Microfil). A single section was chosen from each kidney, and all arteries (n = 1,628) were identified. Intrarenal arteries were largely divisible into two "types," characterized by the presence or absence of a close physical relationship with a paired vein. Arteries with a close physical relationship with a paired vein were more likely to have a larger rather than smaller diameter, and more likely to be in the inner-cortex than the mid- or outer cortex. Computational simulations indicated that direct diffusion of oxygen from an artery to a paired vein can only occur when the two vessels have a close physical relationship. However, even in the absence of this close relationship oxygen can diffuse from an artery to periarteriolar capillaries and venules. Thus AV oxygen shunting in the proximal preglomerular circulation is dominated by direct diffusion of oxygen to a paired vein. In the distal preglomerular circulation, it may be sustained by diffusion of oxygen from arteries to capillaries and venules close to the artery wall, which is subsequently transported to renal veins by convection.
authors.affiliation: Department of Physiology, Monash University, Melbourne, Australia;
authors.forename: Jennifer P
authors.initials: JP
authors.lastname: Ngo
authors.affiliation: School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and.
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Kar
authors.affiliation: Department of Physiology, Monash University, Melbourne, Australia;
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Kett
authors.affiliation: School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Gardiner
authors.affiliation: Department of Physiology, Monash University, Melbourne, Australia; Monash Biomedical Imaging Facility, Monash University, Melbourne, Australia;
authors.forename: James T
authors.initials: JT
authors.lastname: Pearson
authors.affiliation: School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and.
authors.forename: David W
authors.initials: DW
authors.lastname: Smith
authors.affiliation: The University of Adelaide, Adelaide, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Ludbrook
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia;
authors.forename: John F
authors.initials: JF
authors.lastname: Bertram
authors.affiliation: Department of Physiology, Monash University, Melbourne, Australia; Roger.Evans@monash.edu.
authors.forename: Roger G
authors.initials: RG
authors.lastname: Evans
mesh_terms: D000818:Animals; D004058:Diffusion; D007672:Kidney Cortex / Q000098:blood supply*; D008297:Male; D008954:Models, Biological; D010100:Oxygen / Q000097:blood*; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation
chemical_list: D010100:Oxygen
keywords: arterial-to-venous oxygen shunting; arteries; blood vessels; countercurrent diffusion; hypoxia; oxygen transport to tissue