Abstract
Objective: To test the hypothesis that active hyperemia is reduced in skeletal muscle of old rats due to a decreased bioavailability of prostanoids, which in turn is due to increased oxidative stress.
Methods: The microvasculature of the spinotrapezius muscle of 3-, 12-, and 24-month male Sprague-Dawley rats was examined using in vivo videomicroscopy. Arteriolar diameter and centerline red cell velocity were measured in resting and contracting muscle. The effect of prostanoids was examined using indomethacin (10 μ M), and passive resting arteriolar diameters were determined using adenosine (100 μ M). Lipid peroxidation was assessed ex vivo by measuring tissue levels of malondialdehyde.
Results: Arteriolar diameters and blood flow in resting muscle did not differ among the age groups, but increases in diameter and flow during muscle contraction in young rats were greater than in the two older age groups. Indomethacin did not affect resting arteriolar diameters and blood flow in 3- and 12-month rats, but significantly decreased both parameters in 24-month rats. Indomethacin had no effect on arteriolar diameter and blood flow responses during muscle contraction in any age group. Passive resting diameters of arterioles were significantly smaller in 12- and 24-month rats than in 3-month rats. Tissue levels of TBARS were not different among the three age groups.
Conclusions: Arteriolar tone and blood flow in resting skeletal muscle of rats is not altered with age, whereas the increases in these variables that normally accompany muscle contraction are markedly impaired during aging. Neither cyclooxygenase metabolites nor lipid peroxidation appear to be involved in this impairment.
The authors gratefully acknowledge the technical expertise of Kimberly Wix and the assistance of Brandi Conners in this study. This study was supported by National Heart, Lung and Blood Institute grant HL-44012, National Institutes of Health/National Institute on Aging grant 5 R21 AG021510-03, a WVU Health Science Center Internal grant, Office of Research and Graduate Education and by grant RR 16477 from the National Center for Research Resources awarded to the WV Biomedical Research Infrastructure Network.