Studies on vasodilatation in the hand on exposure to heat.

In five subjects whose hands were exposed to heat, no depletion in the plasma kininogen level was observed when vasodilatation occurred. This might be due to the admixture of arterial and venous blood following the opening of arterio-venous (A--V) anastomoses. The small rise obtained by warming was not significant (P greater than 0.1). Consequently, the drop in kinonogen concentration recorded when the hand was allowed to cool to an ambient temperature of 23 degrees C as compared with the basal level and that during the period of warming, was also found to be non-significant. In another nine subjects whose A--V kininogen values were determined when their hands were immersed in a water bath at 37 degrees C, a significant A--V difference of the kininogen content was obtained. From this work, it is concluded that no appreciable depletion of venous kininogen concentration was obtained on hand warming. It is possible that sweat glands, vasodilator nerve fibres and the release of kinins contribute in part to the dilatation that occurs. Possible patho-physiological mechanisms involved are discussed.