The effects of vasodilating drugs and vasoconstrictor nerve stimulation on oxygen uptake in skeletal muscle

Oxygen uptake was studied in skeletal muscle of cat, dog, fox and hare during i.a. infusion of acetylcholine, isoproterenol, and histamine. All agents produced similar effects in the different species. After a brief initial increase, the calculated oxygen uptake returned to near resting levels and remained so throughout the infusion period.

During acetylcholine infusion and concomitant vasoconstrictor nerve stimulation, the oxygen uptake decreased compared to resting levels although blood flow was increased. During motor nerve stimulation, the oxygen uptake increased considerably and acetylcholine infusion did not change the magnitude of that increase.

It is concluded that acetylcholine, isoproterenol, and histamine do not influence the capillary surface area to such an extent as to cause major changes in the oxygen uptake of the resting skeletal muscle. On the other hand, sympathetic vasoconstrictor nerve stimulation decreased oxygen uptake, even during increased blood flow, indicating that under those circumstances the capillary surface area is considerably decreased.