Microvascular oxygen tension in the rat mesentery

• Published in: American journal of physiology. Heart and circulatory physiology 2008-01, Vol.294 (1), p.H21-H28
• Main Authors: Golub, Aleksander S, Barker, Matthew C, Pittman, Roland N
• Format: Article
• Language: English
• Subjects: Animals; Arterioles - metabolism; Blood vessels; Capillaries - metabolism; Female; Injections, Intravenous; Luminescent Measurements; Membranes; Mesentery - blood supply; Mesentery - metabolism; Microscopy; Microscopy - methods; Oxygen; Oxygen - blood; Oxygen - metabolism; Oxygen Consumption; Partial Pressure; Porphyrins - administration & dosage; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Rodents; Signal Processing, Computer-Assisted; Small intestine; Time Factors; Venules - metabolism
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00861.2007

Department of Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia Submitted 23 July 2007 ; accepted in final form 18 October 2007 Longitudinal P O 2 profiles in the microvasculature of the rat mesentery were studied using a novel phosphorescence quenching microscopy technique that minimizes the accumulated photoconsumption of oxygen by the method. Intravascular oxygen tension (P O 2 , in mmHg) and vessel diameter ( d , in µm) were measured in mesenteric microvessels ( n = 204) of seven anesthetized rats (275 g). The excitation parameters were as follows: 7 x 7-µm spot size; 410 nm laser; and 100 curves at 11 pulses/s, with pulse parameters of 2-µs duration and 80-pJ/µm 2 energy density. The mean P O 2 (± SE) was 65.0 ± 1.4 mmHg ( n = 78) for arterioles ( d = 18.8 ± 0.7 µm), 62.1 ± 2.0 mmHg ( n = 38) at the arteriolar end of capillaries ( d = 7.8 ± 0.3 µm), and 52.0 ± 1.0 mmHg ( n = 88) for venules ( d = 22.5 ± 1.0 µm). There was no apparent dependence of P O 2 on d in arterioles and venules. There were also no significant deviations in P O 2 based on d (bin width, 5 µm) from the general mean for both of these types of vessels. Results indicate that the primary site of oxygen delivery to tissue is located between the smallest arterioles and venules (change of 16.3 mmHg, P = 0.001). In conclusion, oxygen losses from mesenteric arterioles and venules are negligible, indicating low metabolic rates for both the vascular wall and the mesenteric tissue. Capillaries appear to be the primary site of oxygen delivery to the tissue in the mesenteric microcirculation. In light of the present results, previously reported data concerning oxygen consumption in the mesenteric microcirculation can be explained as artifacts of accumulated oxygen consumption due to the application of instrumentation having a large excitation area for P O 2 measurements in slow moving and stationary media. microcirculation; phosphorescence quenching microscopy; oxygen partial pressure profiles; oxygen consumption Address for reprint requests and other correspondence: R. N. Pittman, Dept. of Physiology, Medical College of Virginia Campus, Virginia Commonwealth Univ., 1101 E. Marshall St., PO Box 980551, Richmond, VA 23298-0551 (e-mail: pittman{at}vcu.edu )