Hyperglycemia Suppresses the Adrenal Medullary: Response to Hypoxemia

An in vivo microdialysis technique was used to study adrenal medullary function in 6 euglycemic and 6 hyperglycemic anesthetized Sprague-Dawley rats exposed to hypoxia. After stabilization of an adrenal dialysis probe, dialyzable adrenal epinephrine and norepinephrine were measured in response to 15 min of 7.8% oxygen breathing in both groups. In euglycemic rats, hypoxia increased epinephrine and norepinephrine by 650 and 320% above baseline, respectively. During hyperglycemia, (mean plasma glucose level 30.0 mM) epinephrine and norepinephrine rose only 119 and 104%, respectively. The catecholamine increase in the hyperglycemic rats was significantly attenuated in comparison to euglycemic controls (epinephrine, P = 0.0232; norepinephrine, P = 0.0079). These data demonstrate that acute hyperglycemia has the capacity to suppress the normal adrenal medullary response to hypoxemia.