Arteriolar diameter and tissue @entity26 tension during muscle contraction in XXXX @entity35 .

@entity859 @entity101 @entity384 @entity26 @entity35 @entity4095
This study evaluated the possibility that in @entity101 , mechanisms that maintain near normal arteriolar diameters at elevated arteriolar pressures limit the ability of skeletal muscle arterioles to dilate in response to an increase in tissue metabolism. The spinotrapezius muscles of 16- to 20-week-old spontaneously @entity101 @entity35 (SHR) and @entity35 -Kyoto @entity35 (WKY) were contracted at frequencies of 1, 2, 4, and 8 Hz. The inner diameters of first-order through third-order arterioles were measured at rest and following 3 minutes of contractions. Tissue @entity26 tension ( @entity4095 ) at the venous end of capillaries was monitored during 8-Hz contractions. At rest, following contractions, and after maximum dilation with @entity859 , the inner diameters of arterioles of equivalent branch order were not significantly different in SHR and WKY. Opening of closed arterioles during muscle contraction and @entity859 application occurred in less than 5% of the observations in both groups. The resting tissue @entity4095 was 25.5 +/- 1.3 mm Hg in normal @entity35 and 26.1 +/- 2.1 mm Hg in SHR. At nearly maximum vasodilation during 8-Hz stimulation, tissue @entity4095 recovered to 81.9 +/- 12.7% of control in WKY but only to 41.2 +/- 13.0% of control in SHR. These observations indicate that the expression of local regulatory mechanisms related to tissue metabolism is virtually normal in the spinotrapezius muscle vasculature of SHR in the context of @entity384 . However, at near maximum performance, factors other than absolute arteriolar diameter preclude the normal preservation of tissue @entity4095 in the spinotrapezius muscle of SHR.
