BRADYKININ AND FOREARM BLOOD FLOW

Low-dose bradykinin infusion reduces endogenous glucose production in surgical patients

The systemic effect of low-dose bradykinin infusion on total body glucose production and arterial substrate concentrations was examined during D5W infusion (1.0 mg/kg/min) in five normal-weight postsurgical subjects and compared to the response in four saline infused control patients, well matched for age, weight, and degree of postoperative stress. The primed-constant infusion of 6,6-d2-glucose was used to determine the rate of endogenous glucose production. After a basal period of 90 minutes, subjects in the study group were infused with bradykinin at increasing rates of 2.0 and 4.0 micrograms/kg/h, each infusion rate lasting for 90 minutes, whereas in controls corresponding amounts of saline were given. After 75 minutes of bradykinin, endogenous glucose production was significantly reduced as compared to basal values (1.63 +/- 0.21 mg/kg/min, P less than .0125 v 2.20 +/- 0.35 basal). This was accompanied by a significant reduction in arterial concentrations of glucose, lactate, pyruvate, and alanine. Corresponding concentrations of insulin, glucagon, glycerol, free fatty acids, and ketone bodies, as well as mean arterial blood pressure and heart rate was not affected by bradykinin. In the control group no significant changes in substrate and hormone concentrations, or the rate of glucose production were observed. The higher bradykinin infusion rate did not further affect substrate metabolism or systemic hemodynamics. These results demonstrate the inhibitory effect of low-dose bradykinin on glucose production in surgically stressed patients. The stimulation of hepatic prostaglandin synthesis by bradykinin may explain the results since prostaglandins are known to exert an inhibitory effect on hormone stimulated gluconeogenesis and glycogenolysis in liver tissue.

Neurogenic non-adrenergic cutaneous vasodilatation elicited by hypothalamic thermal stimulation in dogs

Hypothalamic heating in dogs with depleted peripheral adrenergic transmitter stores by means of chronic application of reserpine elicits increase of hindpaw blood flow. The vasodilator response is not affected by alpha- and beta-adrenergic or cholinergic blocking substances, nor by histamine-, or prostaglandin-antagonists. Dopamine and ergometrine produce cutaneous vasoconstriction which is antagonized or prevented by haloperidol. The hypothalamic vasodilator response is abolished after intra-arterial injection of haloperidol, after lumbar sympathetic chain section, or by high doses of hexamethonium. The results indicate neurogenic non-adrenergic control of skin blood flow in thermoregulation possibly acting through inhibition of dopaminergic vasoconstrictor mechanisms.

Determination of plasmakinin & kininogen levels in man

1. A method for the estimation of free plasma kinin and kininogen is described, which is suitable for samples of blood taken in hospital.2. The method permits the assay of very low levels of kinin and substantially eliminates errors due to the presence of amines and other interfering substances.3. In normal subjects the mean value of free kinin is 2.8 ng (bradykinin equivalent)/ml. plasma, and 6.1 mug kininogen/ml.4. In vasovagal fainting, carcinoid flush, and dumping syndrome, during the phase of peripheral vasodilatation, the free kinin exceeds 10 ng/ml., and is often in excess of 30 ng/ml.5. Sudden release of free kinin is accompanied by a fall in kininogen level.