Resting blood flow and oxygen consumption in soleus and gracilis muscles of cats

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Abstract
In contrast to previous reports, the results of the present study indicate that vascular responses of isolated soleus muscles of cats are functionally similar to those of gracilis muscles. Vascularly isolated muscles were perfused under free-flow conditions. Venous outflow was measured by a drop counter. Resting blood flows were similar in soleus (n = 16) and gracilis (n = 12) muscles, 6.6 ± 1.2 and 3.8 ± 0.6 ml ⋅ min-1 ⋅ 100 g-1, respectivley (P > 0.05). Resting oxygen consumption averaged 0.26 ± 0.06 and 0.33 ± 0.10 ml O2 ⋅ min-1 ⋅ 100 g-1 for soleus (n = 10) and gracilis muscles (n = 5), respectively (P > 0.05). In four animals, blood flow to soleus muscles measured by the microsphere technique was 2.0 ± 0.3 ml ⋅ min-1 ⋅ 100 g-1 before and 4.6 ± 2.1 ml ⋅ min-1 ⋅ 100 g-1 after isolation of its circulation. Before isolation, blood flow to gracilis muscle was 2.0 ± 0.1 ml ⋅ min-1 ⋅ 100 g-1 after isolation of its circulation. Both soleus and gracilis muscles exhibited active hyperemia. Autoregulation of blood flow in both muscles was weak. However, oxygen supply exceeded demand because oxygen consumption was maintained as blood flow decreased in response to reductions in perfusion pressure. There was no evidence of blood flow-limited oxygen consumption. Thus, the soleus muscles of the present study not only have low-resting blood flows and oxygen consumptions, but their responses to physiological stimuli are similar to those of gracilis muscles.