Vasopressin and angiotensin II stimulate oxygen uptake in the perfused rat hindlimb

Vasopressin and angiotensin II markedly stimulated oxygen uptake in the perfused rat hindlimb. The increase due to each agent approached 70% of the basal rate, and was greater than that produced by a maximal concentration of norepinephrine. Half-maximal stimulation occurred at 60 pM vasopressin, 0.5 nM angiotensin II and 10 nM norepinephrine. Angiotensins I and III were less potent than angiotensin II. For each agent, the dose-dependent increase in oxygen uptake coincided with a dose-dependent increase in perfusion pressure. The effects of both vasopressin and angiotensin to increase oxygen uptake and pressure were not inhibited by either phentolamine, propranolol or a combination of the two, but were completely inhibited by the vasodilator, nitroprusside. Nitroprusside also inhibited flow-induced increases in hindlimb oxygen uptake and perfusion pressure. The findings indicate a key role for the vascular system in the control of hindlimb oxygen uptake.