Determination of plasma kinin and 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.