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DEVELOPMENTAL PHYSIOLOGY AND PREGNANCY

Effects of age on brachial artery myogenic responses in humans

¹Division of Cardiology, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey 17033; and ²Lebanon Veterans Affairs Medical Center, Lebanon, Pennsylvania 17042

Submitted 22 October 2003 ; accepted in final form 17 May 2004

The myogenic response, the inherent ability of blood vessels to rapidly respond to changes in transmural pressure, is involved in local blood flow autoregulation. Animal studies suggest that aging impairs the myogenic response. The purpose of this study was to compare the effects of changes in transmural pressure on mean blood velocity (MBV, cm/s) in young and older subjects. Twelve younger men and women (25 ± 1 yr) were gender and body composition matched to twelve older men and women (65 ± 1 yr). A specially designed tank raised or lowered forearm pressure by 50 mmHg within 0.2 s. Brachial artery MBV was measured directly above the site of forearm pressure change using Doppler methods. In response to increasing transmural pressure (i.e., release of +50 mmHg), older subjects compared with younger subjects had significantly lower peak MBV ( 12.43 ± 1.16 vs. 17.97 ± 2.01 cm/s; P < 0.05), reduced rates in the dynamic fall of MBV after peak values were achieved (vasoconstriction) (–1.88 ± 0.17 vs. –2.90 ± 0.28 cm·s^–1·s^–1; P < 0.05), and lower MBV values with sustained suction. In response to decreasing transmural pressure (i.e., change to +50 mmHg), there was a significantly greater increase in MBV ( peak flow from trough 7.71 ± 1.32 vs. 4.38 ± 0.71 cm/s; P < 0.05) and a trend toward a greater rate of rise in MBV (vasodilation; 1.61 ± 0.29 vs. 0.96 ± 0.21 cm·s^–1·s^–1; P = 0.08) in the older subjects. Older subjects compared with the younger subjects exhibited decreased dynamic vasoconstriction, enhanced steady-state constriction, as well as evidence for enhanced dynamic vasodilation responses to sustained alterations in forearm transmural pressure.

regional blood flow; blood pressure; circulation

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