Variations in the response of different arteries to blood serum and plasma

Abstract

Recent work by Brodie, Sollmann, and O'Connor has shown that the blood contains substances acting on the vasomotor apparatus other than suprarenin. Even before the work of these investigators it had been noticed by Stevens and Lee that the use of defibrinated blood for the perfusion of isolated organs was often unsatisfactory because of the gradual diminution in outflow. This was not investigated thoroughly until 1900 by Brodie. He observed that the injection of blood serum into the jugular vein of a cat caused an immediate fall in blood pressure. The cat's own serum was as efficient in this respect as the serum of any other animal. The cat, however, is the only animal which responds in this manner, for Brodie's experiments were negative on the dog and rabbit. The mechanism in this case appears to be a reflex inhibition of the vasomotor center from excitation of the pulmonary branches of the vagus. The importance of Brodie's work lies in the fact that he was the first to show that plasma and serum are not identical in their physiological activities, for, whereas the effect just described is produced by serum, plasma is entirely inactive. The process of clotting liberates some substance to which this action is to be attributed.

It was probably these experiments of Brodie which guided O'Connor in the analysis of the constrictor effect produced by blood serum on the hind limbs of the frog. He was able to show that the constriction produced by serum is not entirely due to its suprarenin content. Another substance comes into play which causes constriction and which is present only in the serum.

We have investigated the vasomotor effect of plasma and serum in different vessels of the body, especially in regard to their mode of action.