|
|
||||||||
Departments of Physiology and Veterinary Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211
The purpose of this study
was to test the hypothesis that endothelium-dependent dilation is
impaired in soleus resistance arteries from hindlimb-unweighted (HLU)
rats. Male Sprague-Dawley rats (300-350 g) were exposed to HLU
(n = 14) or weight-bearing control (Con,
n = 14) conditions for 14 days. After the 14-day treatment period, soleus first-order (1A) arterioles were isolated and
cannulated with micropipettes to assess vasodilator responses to an
endothelium-dependent dilator, ACh
(10
9-10
4 M), and an
endothelium-independent dilator, sodium nitroprusside (SNP,
10
9-10
4 M). Arterioles from HLU rats
were smaller than Con arterioles (maximal passive diameter = 140 ± 4 and 121 ± 4 µm in Con and HLU, respectively) but
developed similar spontaneous myogenic tone (43 ± 3 and 45 ± 3% in Con and HLU, respectively). Arteries from Con and HLU rats
dilated in response to increasing doses of ACh, but dilation was
impaired in arterioles from HLU rats (P = 0.03), as was
maximal dilation to ACh (85 ± 4 and 65 ± 4% possible
dilation in Con and HLU, respectively). Inhibition of nitric oxide (NO)
synthase (NOS) with
N
-nitro-L-arginine (300 µM)
reduced ACh dilation by ~40% in arterioles from Con rats and
eliminated dilation in arterioles from HLU rats. The cyclooxygenase
inhibitor indomethacin (50 µM) did not significantly alter dilation
to ACh in either group. Treatment with
N
-nitro-L-arginine + indomethacin eliminated all ACh dilation in Con and HLU rats. Dilation
to sodium nitroprusside was not different between groups
(P = 0.98). To determine whether HLU decreased expression of endothelial cell NOS (ecNOS), mRNA and protein levels were measured in single arterioles with RT-PCR and immunoblot analysis.
The ecNOS mRNA and protein expression was significantly lower in
arterioles from HLU rats than in Con arterioles (20 and 65%,
respectively). Collectively, these data indicate that HLU impairs ACh
dilation in soleus 1A arterioles, in part because of alterations in the
NO pathway.
skeletal muscle; microcirculation; acetylcholine; microgravity; physical inactivity; indomethacin; N
-nitro-L-arginine
This article has been cited by other articles:
![]() |
M. D. Delp Unraveling the complex web of impaired wound healing with mechanical unloading and physical deconditioning J Appl Physiol, May 1, 2008; 104(5): 1262 - 1263. [Full Text] [PDF] |
||||
![]() |
C. R. Woodman, D. Ingram, J. Bonagura, and M. H. Laughlin Exercise training improves femoral artery blood flow responses to endothelium-dependent dilators in hypercholesterolemic pigs Am J Physiol Heart Circ Physiol, June 1, 2006; 290(6): H2362 - H2368. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. W. P. Bleeker, P. C. E. De Groot, G. A. Rongen, J. Rittweger, D. Felsenberg, P. Smits, and M. T. E. Hopman Vascular adaptation to deconditioning and the effect of an exercise countermeasure: results of the Berlin Bed Rest study J Appl Physiol, October 1, 2005; 99(4): 1293 - 1300. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. J. Mueller, C. M. Foley, and E. M. Hasser Hindlimb unloading alters nitric oxide and autonomic control of resting arterial pressure in conscious rats Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2005; 289(1): R140 - R147. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. W. P. Bleeker, M. Kooijman, G. A. Rongen, M. T. E. Hopman, and P. Smits Preserved contribution of nitric oxide to baseline vascular tone in deconditioned human skeletal muscle J. Physiol., June 1, 2005; 565(2): 685 - 694. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. C. E. de Groot, F. Poelkens, M. Kooijman, and M. T. E. Hopman Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals Am J Physiol Heart Circ Physiol, July 1, 2004; 287(1): H374 - H380. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. A. Spier, M. D. Delp, C. J. Meininger, A. J. Donato, M. W. Ramsey, and J. M. Muller-Delp Effects of ageing and exercise training on endothelium-dependent vasodilatation and structure of rat skeletal muscle arterioles J. Physiol., May 1, 2004; 556(3): 947 - 958. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. G. Crandall, M. Shibasaki, T. E. Wilson, J. Cui, and B. D. Levine Prolonged head-down tilt exposure reduces maximal cutaneous vasodilator and sweating capacity in humans J Appl Physiol, June 1, 2003; 94(6): 2330 - 2336. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Ma, C. I. Kahwaji, Z. Ni, N. D. Vaziri, and R. E. Purdy Effects of simulated microgravity on arterial nitric oxide synthase and nitrate and nitrite content J Appl Physiol, January 1, 2003; 94(1): 83 - 92. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Freeman, V. Lirofonis, W. B. Farquhar, and M. Risk Limb venous compliance in patients with idiopathic orthostatic intolerance and postural tachycardia J Appl Physiol, August 1, 2002; 93(2): 636 - 644. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. G. Schrage, C. R. Woodman, and M. H. Laughlin Mechanisms of flow and ACh-induced dilation in rat soleus arterioles are altered by hindlimb unweighting J Appl Physiol, March 1, 2002; 92(3): 901 - 911. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. L. Heaps and D. K. Bowles Nonuniform changes in arteriolar myogenic tone within skeletal muscle following hindlimb unweighting J Appl Physiol, March 1, 2002; 92(3): 1145 - 1151. [Abstract] [Full Text] [PDF] |
||||
![]() |
L.-F. Zhang Vascular adaptation to microgravity: what have we learned? J Appl Physiol, December 1, 2001; 91(6): 2415 - 2430. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. R. Woodman, W. G. Schrage, J. W. E. Rush, C. A. Ray, E. M. Price, E. M. Hasser, and M. H. Laughlin Hindlimb unweighting decreases endothelium-dependent dilation and eNOS expression in soleus not gastrocnemius J Appl Physiol, September 1, 2001; 91(3): 1091 - 1098. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |