Direct evidence that an increase in aortic norepinephrine level in response to insulin-induced hypoglycemia is due to increased adrenal norepinephrine output

This study reports on the major source of circulating norepinephrine that is known to increase, progressively, during sustained hypoglycemia induced by intravenous insulin administration. Plasma concentrations of epinephrine, norepinephrine, and dopamine were simultaneously determined for adrenal venous and aortic blood in dogs anesthetized with sodium pentobarbital. The model used allowed us to perform a functional adrenalectomy (ADRX), while continuously monitoring the adrenal medullary secretory function. Under basal conditions, the net output (μg/min) of adrenal epinephrine, norepinephrine, and dopamine were 0.169 ± 0.074, 0.067 ± 0.023, and 0.011 ± 0.003, respectively. Plasma concentrations (ng/mL) of aortic epinephrine, norepinephrine, and dopamine were 0.132 ± 0.047, 0.268 ± 0.034, and 0.034 ± 0.009. Following insulin injection (0.15 IU/kg, i.v.), the net output (μg/min) of adrenal epinephrine, norepinephrine, and dopamine increased gradually (p < 0.05), reaching the values of 0.918 ± 0.200, 0.365 ...