Escherichia coli endotoxin reduces cytochrome aa(3) redox status in pig skeletal muscle

Objective: To assess the effect of endotoxin on cytochrome aa(3) (Caa(3)) r edox status in a controlled blood flow preparation of pig isolated hindlimb , at a constant oxygen delivery ((D) over dotO(2limb)) (constant flow perio d) and during progressive ischemia (decreasing flow period). Design: Randomized, controlled experimental study. Setting: University hospital experimental laboratory. Subjects: Ten piglets. Interventions: Hindlimb blood flow was restricted to the femoral vessels. T he arterial femoral blood flow coming from the carotid artery was controlle d by a roller occlusive pump. The femoral venous blood flow was returned to the jugular vein. During the first 100 mins, the hindlimb blood flow was m aintained at a normal level and then decreased stepwise. Animals were rando mized to receive 150 mu g/kg endotoxin lipopolysaccharide (LPS; n = 5) or s aline (control; n = 5). Measurements and Main Results: Hindlimb muscle Caa(3) redox status was moni tored by near-infrared spectroscopy, Hindlimb (D) over dotO(2limb) and oxyg en consumption ((V) over dotO(2limb)) were calculated. In the LPS group, a rapid reduction of Caa(3) redox status was observed after LPS administratio n, whereas the hindlimb blood flow remained normal with no change in (D) ov er dotO(2limb) and (V) over dotO(2limb). A progressive simultaneous decreas e in (D) over dotO(2limb) and (V) over dotO(2limb) was observed during the decreasing flow period with no further reduction in Caa(3) redox status. In the control group, no change was observed in Caa(3), (D) over dotO(2limb), or (V) over dotO(2limb) during the constant flow period. During the decrea sing flow period, Caa(3) redox status was reduced as (D) over dotO(2limb) a nd (V) over dotO(2limb) decreased. Conclusion: Our results suggest that endotoxin may induce a reduction of Ca a(3) redox status independently of (D) over dotO(2) and (V) over dotO(2).