Bradykinin and Human Forearm Metabolism: Inhibition of Endogenous Prostaglandin Synthesis

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Abstract
Human forearm metabolism was studied in healthy volunteers by registration of arterial and deep-venous concentrations of oxygen and glucose and of resting forearm blood flow during the intrabrachial arterial infusion of 0.9% NaCl (n = 4), papaverine (n = 5), bradykinin (n = 9) and bradykinin after the oral indomethacin pretreatment (n = 10). Blood flow was not affected during NaCl (0.2 ml/min) infusion but increased, depending on the concentrations, 2- and 3-fold during papaverine (2 or 3 .mu.g/(kg .times. min)) infusion, and 2-fold during bradykinin (0.2 ng/(kg .times. min)) infusion. The latter effect on the blood flow was significantly smaller when endogenous prostaglandin [PG] synthesis was impaired by indomethacin pretreatment. Arterial oxygen and glucose concentrations were maintained during the individual infusions. This was also true for the arterial-deep-venous concentration differences of oxygen and glucose during NaCl infusions. Corresponding to the acceleration of the blood flow caused by papaverine and bradykinin, arterial-deep-venous concentration oxygen differences declined, indicating that oxygen consumption of the muscle was not changed. A similar behavior was observed for muscular extraction, and consequently glucose uptake when blood flow acceleration was caused by papaverine. Doubling of blood flow caused by bradykinin infusion was accompanied with enlargement of the arterial-deep-venous concentration difference and thus of muscular glucose uptake. There was no change in arterial and forearm deep-venous insulin levels under these conditions. This effect of bradykinin was nearly abolished after oral indomethacin pretreatment. Apparently bradykinin affects the glucose metabolism of the human forearm apparently via endogenously synthesized PG.