Human Epinephrine Secretion. Direct Measurement of the Secretion of Epinephrine from the Human Adrenal Medulla1

Direct measurements of the secretion of epinephrine from the human adrenal medulla was achieved in conscious patients by the selective catheterization of the left adrenal vein and the analysis of left adrenal vein plasma for norepinephrine and epinephrine. There was an extreme variability in epinephrine secretory rates within the same individual at different points in time as well as variability in epinephrine secretory rates between individuals. It could not be shown that these apparently spontaneous fluctuations in epinephrine secretory rate were due to the injection of angiography dye, changes in the adrenal plasma flow rates, or the experience of pain. They may be due to an intermittent mode of secretion of epinephrine. The data revealed that the human adrenal medulla can selectively release epinephrine without the concomitant release of significant amounts of norepinephrine. The data suggest that normally less than 1% of the epinephrine secreted by the adrenal medulla in a 6-hr period will appear in the urine as free epinephrine. There was a positive correlation between epinephrine secretory rates and simultaneous aortic plasma epinephrine concentrations. However, this was statistically insignificant.