Resting and postcontraction blood flow in slow and fast muscles of the chick during development

Abstract

Blood flow, oxygen consumption, and carbon dioxide output were studied in the slow (latissimus dorsi anterior-ALD) and fast (latissimus dorsi posterior-PLD) muscles in young chicks and adult leghorns and in slow (soleus) and fast (gastrocnemius) muscles in cats at rest and after tetanic contraction. Resting blood flow, measured by a drop counter applied to the venous outflow, was in adult leghorns three times higher in slow muscles as compared with fast muscles. Similar changes were also found in oxygen consumption and CO 2 output. In the cat soleus, blood flow at rest was up to ten times higher than in the gastrocnemius, and the same difference was observed in oxygen consumption and CO 2 output. The respective A-V differences were not significantly different. The differences in blood flow are established during development and appear considerably later than the differences in the speed of contraction and enzyme activity. In 8-day-old chicks (in which the enzyme pattern already resembles that in adult birds; i.e., oxidative enzymes have high activities in slow, glycolytic in fast muscles) blood flow measured by 133Xe clearance did not differ in the two types of muscle. In 10-day-old chicks a slightly higher blood flow was observed in the slow as compared with the fast muscles. In 28-day-old chicks, flow in slow muscles was 60% higher, and this pattern is also seen in adult leghorns. During the postcontraction period (after 20–30 sec tetanic contraction) blood flow was always increased in fast muscles. In slow muscles the increase in flow measured by 133Xe clearance was similar to that in fast muscles only in 10-day-old chicks. The increase was much smaller in 28-day-old chicks, and altogether absent in adults. The flow measured by drop counter was slightly increased in the postcontraction period even in slow muscles; however, this increase was significantly smaller than in fast muscles.