Effects of eccentric exercise on microcirculation and microvascular oxygen pressures in rat spinotrapezius muscle

• Published in: Journal of applied physiology (1985) 2005-10, Vol.99 (4), p.1516-1522
• Main Authors: Kano, Yutaka, Padilla, Danielle J, Behnke, Brad J, Hageman, K. Sue, Musch, Timothy I, Poole, David C
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Blood Flow Velocity; Capillaries; Circulatory system; Erythrocyte Volume; Exercise; Female; Fundamental and applied biological sciences. Psychology; Microcirculation; Motor Activity - physiology; Muscle, Skeletal - blood supply; Muscular system; Oxygen; Oxygen - blood; Partial Pressure; Rats; Rats, Sprague-Dawley; Rodents
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00069.2005

1 Departments of Anatomy and of Physiology and Kinesiology, Kansas State University, Manhattan, Kansas; and 2 Departments of Health and Kinesiology, Texas A&M University, College Station, Texas Submitted 20 January 2005 ; accepted in final form 24 June 2005 A single bout of eccentric exercise results in muscle damage, but it is not known whether this is correlated with microcirculatory dysfunction. We tested the following hypotheses in the spinotrapezius muscle of rats either 1 (DH-1; n = 6) or 3 (DH-3; n = 6) days after a downhill run to exhaustion (90–120 min; –14° grade): 1 ) in resting muscle, capillary hemodynamics would be impaired, and 2 ) at the onset of subsequent acute concentric contractions, the decrease of microvascular O 2 pressure (P mv O 2 ), which reflects the dynamic balance between O 2 delivery and O 2 utilization, would be accelerated compared with control (Con, n = 6) rats. In contrast to Con muscles, intravital microscopy observations revealed the presence of sarcomere disruptions in DH-1 and DH-3 and increased capillary diameter in DH-3 (Con: 5.2 ± 0.1; DH-1: 5.1 ± 0.1; DH-3: 5.6 ± 0.1 µm; both P < 0.05 vs. DH-3). At rest, there was a significant reduction in the percentage of capillaries that sustained continuous red blood cell (RBC) flux in both DH running groups (Con: 90.0 ± 2.1; DH-1: 66.4 ± 5.2; DH-3: 72.9 ± 4.1%, both P < 0.05 vs. Con). Capillary tube hematocrit was elevated in DH-1 but reduced in DH-3 (Con: 22 ± 2; DH-1: 28 ± 1; DH-3: 16 ± 1%; all P < 0.05). Although capillary RBC flux did not differ between groups ( P > 0.05), RBC velocity was lower in DH-1 compared with Con (Con: 324 ± 43; DH-1: 212 ± 30; DH-3: 266 ± 45 µm/s; P < 0.05 DH-1 vs. Con). Baseline P mv O 2 before contractions was not different between groups ( P > 0.05), but the time constant of the exponential fall to contracting P mv O 2 values was accelerated in the DH running groups (Con: 14.7 ± 1.4; DH-1: 8.9 ± 1.4; DH-3: 8.7 ± 1.4 s, both P < 0.05 vs. Con). These findings are consistent with the presence of substantial microvascular dysfunction after downhill eccentric running, which slows the exercise hyperemic response at the onset of contractions and reduces the P mv O 2 available to drive blood-muscle O 2 delivery. skeletal muscle; downhill running; microvascular adaptation; capillary hemodynamics; oxygen exchange Address for reprint requests and other correspondence: D. C. Poole, Dept. of Anatomy and Physiology, College of Veterinary Medicine, 228 Coles