The influence of certain conditions on the rate at which epinephrin is liberated from the adrenals into the blood

Abstract

1. By means of the rabbit intestine and uterus segment tests, we have obtained further evidence that, under our experimental conditions at any rate, the rate of discharge of epinephrin into the blood of the adrenal veins is relatively steady and not easily influenced by such procedures as we have tried; for example, stimulation of the afferent fibers in large peripheral nerves (sciatic and brachial) or asphyxia. This is not because the discharge is already maximal owing to the necessary conditions of the experiment (trauma, anesthesia, etc.). For, by electrical stimulation of the cut splanchnic, the rate of liberation can be made decidedly greater than the rate of spontaneous liberation with intact splanchnics.

2. Unlike the rate of liberation per unit of time, the concentration of epinephrin in the adrenal vein blood can be observed to vary decidedly in the course of an experiment, increasing, in general, as the rate of blood flow decreases. This can be shown by collecting adrenal vein blood in successive samples. When the blood flow slackens, owing to hemorrhage or other circumstances, the earlier specimens will be found to contain a smaller concentration of epinephrin than the later specimens.

For example, in a dog, weighing 10 kg., the first sample from the cava pocket, into which the adrenal veins were alone discharging, flowed at the rate of 8 C.C. per minute, the second sample 7.2 c.c., third 5.8 c.c., fourth 4.4 c.c., fifth 3.2 c.c., sixth 2.4 c.c., seventh 1.5 C.C. A definite increase in the epinephrin concentration in the successive samples was clearly shown by the intestine and especially by the uterus tests. The concentration was assayed in the first sample at somewhat more than I : 3,300,000; in the third sample at somewhat more than I : 1,670,000; in the seventh sample at somewhat less than I : 750,000.