Oxygen consumption in resting dog gracilis muscle perfused at varying oxygen delivery

The different response of O2 uptake (VO2) of resting skeletal muscle to the changes in blood flow has been thought to reflect a species difference. To scrutinize this notion, we investigated the relation between O2 delivery (arterial O2 content multiplied by blood flow) and VO2 in isolated dog gracilis muscle perfused solely with normal hematocrit (Ht) blood (n = 9), or alternately with normal and low Ht blood (n = 6), or alternately with normal and high Ht blood (n = 3) at varying perfusion rates. Eleven out of the 18 preparations showed an autoregulation of blood flow, and the others did not. But, in all preparations, the VO2 was delivery-independent above a critical O2 delivery (0.45 ml/(min.100 g muscle)) and showed the constant VO2 of 0.30 ml/(min.100 g), while below the critical level it turned out to be delivery-dependent. The maximal extraction ratio was 0.67. The same relationship was found with the low and high Ht perfusion. The pattern observed in dog gracilis muscle was essentially the same as that in rat gracilis muscle (KOLAR and JANSKY, 1984).