Muscle venous PO2 and VO2 are linearly related in repetitive tetanic contractions of canine muscle during hypoxic hypoxia

1. It has previously been shown that perfusion with high O-2-affinity-eryth rocytes decreases venous PO2 (PVO2) and decreases O-2 uptake ((V) over dot O-2) in contracting muscle at the same O-2 delivery (arterial Oz concentrat ion x flow). A linear (V) over dot O-2-PVO2 relationship has been obtained with a (V) over dot O-2-axis intercept, suggesting that, during this type o f hypoxia, (V) over dot O-2 is composed of a PVO2-dependent and -independen t (V) over dot O-2. However, the (V) over dot O-2-PVO2 relation during hypo xic hypoxia has not been examined. 2. To clarify this relation, PVO2 and (V) over dot O-2 have been measured i n contracting gastrocnemius (1 Hz trains of 0.2s isometric tetani) under bo th normoxic and hypoxic conditions during 5 min of stimulation. 3. Venous O-2 changes proportionally with Oz delivery, Each (V) over dot O- 2-PVO2 relation was linear, with the mean described by the equation (V) ove r dot O-2 = 5.06 + 0.41 x PVO2 (n = 6, r = 0.81, P <0.05). The (V) over dot O-2-axis intercept was significantly different from zero (P <0.05). 4. These results were similar to those obtained during hypoxia induced by h igh O-2-affinity-erythrocytes. We conclude that there is a linear relations hip between PVO2 and (V) over dot O-2 above the (V) over dot O-2-axis inter cept, regardless of the type of hypoxia.