Plasma Epinephrine Disturbances in Diabetic Subjects during Standing and after Isometric Exercise*

Effects of isometric exercise on plasma norepinephrine (NE), epinephrine (E), and related factors (mean +/- SE) were studied in 10 healthy, insulin-dependent diabetic subjects and 10 matched control adults. Measurements were obtained after 30 min of bedrest and sequentially during 10 min of upright posture and 5 min of handgrip and after 15 min of rest while still upright. In control and diabetic groups, respectively, basal plasma NE (180 +/- 22 vs. 169 +/- 27 pg/ml) and E (24 +/- 4 vs. 33 +/- 8 pg/ml) as well as heart rate and mean blood pressure did not differ. However, E responses to standing and recovery from isometric exercise in diabetic subjects significantly exceeded control values 2-fold (P less than 0.05) and were accompanied by exaggerated increases in heart rate (P less than 0.05); whereas NE, mean blood pressure, plasma GH, and glucagon profiles during all periods were not significantly different. Exaggerated E responses in diabetic patients were associated with plasma glucose increments above resting values during grip and recovery of 21 and 41 mg/dl, respectively; slightly though significantly higher plasma cortisol responses, and low, fixed concentrations of plasma insulin. These findings contrasted to corresponding glucose increments in control subjects of only 3-4 mg/dl and a 2-fold rise in plasma insulin during recovery. It is concluded that E disturbances in this diabetic group after standing and isometric exercise are physiologically linked to abnormal increments in heart rate and plasma glucose concentrations. These observations suggest that altered E, as opposed to NE, may represent an early defect of the sympathoadrenal system in diabetes mellitus.