Hemorrhage Hypotension Influences on Plasma Glucose Concentration: A New Approach for Evaluating Baroreflex Effects on Metabolic Adjustments

The present study shows that hyperglycemic response to hemorrhage is an easy method for evaluating metabolic adjustments in normal rats and in other models that show autonomic and metabolic imbalances. In this regard, the baroreflex control of hyperglycemic response induced by hemorrhage hypotension was evaluated by removing blood through the jugular catheter (1.2 mL/100g b.w./ 2 min). Blood samples (0.2mL) were collected immediately before hemorrhage and at 5, 10, 20 and 30 minutes after hemorrhage [1, 2]. In addition, the baroreflex control of heart rate was assessed by pharmacological test, using intravenous doses of phenylephrine hydrochloride (PE, 10 μg/mL) and sodium nitroprusside (SNP, 10 μg/mL) in random order. Heart rate and blood pressure were measured through the insertion of a polyethylene catheter inserted into the abdominal aorta through the left femoral artery. The derived variables of baroreflex control to heart rate and hemorrhage hyperglycemia response were measured according to the following equation: Y = A1/{1+ exp[A2(X - A3)]} + A4. The evaluation of a new approach for studying the baroreflex effects on metabolic adjustments was done with animals fed with a hypercaloric diet. Hypercaloric diet induced an upward shift in the baroreflex curve to heart rate (p<0.05) and an increased heart rate reflex due to the change in MAP during the operating range (p<0.05). It also shifted the baroreflex curve to a higher level of hyperglycemic response to hemorrhage (p<0.05), as well as, increased maximal gain (p<0.05) and augmented hyperglycemic response to hemorrhage hypotension during the operating range (p<0.05). Therefore, we propose that the baroreflex control of hyperglycemic response should be a useful tool for evaluating metabolic dysfunction related to hemorrhage in models of animals that show autonomic imbalance, such as malnutrition, hypertension, diabetes and obesity.