Response of extraparenchymal resistance arteries of rat skeletal muscle to reduced PO2

Abstract

Isolated resistance arteries from the gracilis muscle of rats were simultaneously perfused and superfused with physiological salt solution (PSS) equilibrated with control (21% O2) and reduced (15, 10, 5, or 0% O2) concentrations of O2. The vessels exhibited a significant dilation in response to reduced PO2, which could be inhibited by selective perfusion of the lumen with 21% O2 PSS, endothelial removal, and 1 microM indomethacin, but was unaffected by the nitric oxide synthase inhibitor N omega-nitro-L-arginine (10 microM). Contraction of the arteries in response to 50 mM K+ was inhibited by 0% O2, whereas agonist (norepinephrine and serotonin)-induced contractions and pressure-induced myogenic responses were insensitive to reduced PO2. These results suggest that 1) skeletal muscle resistance arteries are intrinsically sensitive to reduced PO2 independent of parenchymal cell influences, 2) inhibition of resting tone in these vessels is mediated by an endothelium-derived product of the cyclooxygenase pathway, and 3) various forms of contractile activation are not equally sensitive to inhibition by reduced PO2 in extraparenchymal resistance arteries of skeletal muscle.

Increased peripheral vascular disease risk progressively constrains perfusion adaptability in the skeletal muscle microcirculation

“…As has been demonstrated previously for the experimental conditions of the present study, all of the conditions of elevated PVD risk were associated with an impaired endothelial function, as evidenced by a reduced upper bound of the acetylcholine concentration-response relationship (9,17,19,24,33,34,39,49,58), although the degree of impairment was similar in magnitude regardless of the severity of the PVD risk score. However, the contribution of oxidant stress to each condition of PVD risk was more variable, with some of the states of more severe PVD risk showing a robust role for oxidant stress in compromising endothelial function while others demonstrated a more modest or minimal contribution.…”

“…Vessel diameter was measured with television microscopy and an on-screen video micrometer. Arterioles were extended to their in situ length and were equilibrated at 80% of the animal's mean arterial pressure (19).…”

High-salt diet impairs vascular relaxation mechanisms in rat middle cerebral arteries

“…This dual perfusion/superfusion system allows extravascular gas concentrations, luminal gas concentrations, and intravascular pressure to be controlled simultaneously (6,7). Vessel diameters were measured via television microscopy and a video micrometer system.…”

“…In another series of experiments, VSM transmembrane potentials (Em) were measured with a high-impedance amplifier and glass microelectrodes (40-80 M⍀ impedance) filled with 3 M KCl, as previously described (6,7,18,20,37). Criteria for a successful impalement included an abrupt drop to a steady level of E m for a minimum of 5 s and an abrupt return to baseline on exit of the electrode from the cell.…”

“…Perfusate PO 2 was reduced by bubbling the PSS in the perfusion reservoir with the same gas mixture and by using gasimpermeable delivery lines. These procedures result in a reduction of both perfusate and superfusate PO2 from the control value of ϳ140 torr during 21% O2 perfusion/superfusion to ϳ40-45 torr during equilibration of the perfusion and superfusion reservoirs with the 0% O2 gas mixture (6).…”