AGING DECREASES MYOGENIC RESPONSIVENESS OF RAT SKELETAL MUSCLE ARTERIOLES

Abstract

467 Aging produces decrements in cardiovascular function and in skeletal muscle work capacity. Aging-induced impairment of skeletal muscle work capacity may be related to alterations in local control of and decreased blood flow to skeletal muscle. Specifically, a reduction in the distensible elements of the arteriolar wall may alter the intrinsic vasoactive responses of resistance vessels to changes in intraluminal pressure, the myogenic response. The purpose of this study was to test the hypothesis that aging alters the myogenic responsiveness of skeletal muscle arterioles. 1A arterioles were isolated from the gastrocnemius of 4 month old and 24 month old Fischer rats. The arterioles were cannulated and pressurized via hydrostatic reservoirs in the absence of intraluminal flow. Diameter changes were determined in response to stepwise increases in intraluminal pressure (10 - 100 cm H2O, in 10 cm H2O increments). Active vasoconstriction to increases in pressure were significantly decreased in arterioles isolated from aged rats. In contrast, vasoconstrictor responses to norepinephrine (NE, 10−9 - 10−4 M) tended to be augmented in arterioles from aged animals. These data indicate that aging produces specific adaptations of skeletal muscle arterioles resulting in decreased responsiveness to changes in intraluminal pressure. Supported by AHA, Texas Affiliate Grant 98BG-801 and NASA NAGW-4842, NAG5-3754.