Role of oxygen in autoregulation of blood flow in isolated vessels

Abstract

The role of oxygen in control of local blood flow was investigated in isolated arterial segments 1 cm in length and 0.5–1.0 mm in diameter by perfusion with blood of various Po2 levels. A decrease in vascular resistance always occurred when the Po2 was lowered and an increase occurred when it was raised. In 20 vessels, using constant-pressure perfusion, an average increase in conductance of 2.38 times normal level was obtained when the Po2 was lowered from 100 to 30 mm Hg. When this datum was plotted according to initial flow, the smaller vessels gave the greatest response to low oxygen (2.73 times normal; sem ± 0.15), whereas the largest gave the least (1.76 times normal; sem ± 0.10). Forty-three vessels perfused under constant-flow conditions gave results which were consistent with and confirmed the constant-pressure results. In all of these experiments pH, Pco2, and temperature were monitored and kept at physiological levels. The results indicate that oxygen could well be a factor in the autoregulation of blood flow.

Role of endothelium-derived prostaglandins in hypoxia-elicited arteriolar dilation in rat skeletal muscle.

“…In vitro studies of isolated blood-perfused skeletal muscle arteries (0.5-1 mm in diameter) indicated a direct effect of decreases in oxygen tension on vascular tone3 and a greater sensitivity of the smaller (0.5 mm in diameter) compared with the larger arteries to the changes in oxygen tension. 4 Decreases in vascular tone associated with decreases in oxygen tension have also been reported to occur in large vessels such as the aorta,5 carotid artery,6 and isolated intestinal3 and coronary7, 8 arteries. Taken together, these studies indicate that large blood vessels are sensitive to changes in oxygen The direct effects of oxygen and the response of arterioles to changes in oxygen tension are not completely understood.…”

Effect of hypoxia on force, intracellular pH and Ca2+ concentration in rat cerebral and mesenteric small arteries.

“…Wadsworth, 1994). The mechanisms responsible for the reduction of blood vessel tone induced by hypoxia are not completely known (Carrier, Walker & Guyton, 1964;Hellstrand, Johansson & Norberg, 1977;Coburn, Grubb & Aronson, 1979;L6vgren & Hellstrand, 1985; Smeda, Madden & Harder, 1986;Rodman, Hasunuma, Peach & McMurtry, 1990; Beckerath, Cyrys, Dischner & Daut, 1991). L6vgren & Hellstrand (1987& Hellstrand ( , 1988 concluded that the inhibition of active tone in the isolated portal vein by a reduction in the partial pressure of oxygen (PO2) is unlikely to result from an increase in the lactate concentration or a fall in phosphocreatinine levels in the vascular smooth muscle cells.…”

The oxygen sensitivity of hamster cheek pouch arterioles. In vitro and in situ studies.

“…As a result, most investigators have tried to evaluate the two possibilities by studying the oxygen sensitivity of vascular smooth muscle in strips, rings, or segments of relatively large conduit or elastic arteries in vitro (Carrier et al, 1964;Pittman and Duling, 1973;Coburn et al, 1979;Chang and Detar, 1980). Whereas these investigations have shown that arteries are sensitive to changes in Po 2 , their relevance to arteriolar oxygen sensitivity and to the role of oxygen in the local control of blood flow remains in question.…”