Cyclic AMP and metabolic substrates following hemorrhage in awake and anesthetized rats

The levels of several metabolites in plasma were studied during a period of 4 h in awake and barbiturate anesthetized rats after a blood volume loss of approximately 3% of b.w. Blood pressure was 70 mmHg (9.3 kPa) in the awake and 35 mmHg (4.7 kPa) in the anesthetized rats. Resting levels of plasma glucose, blood lactate and pyruvate and plasma cyclic AMP were higher in the awake rats than in the anesthetized rats. Bleeding caused an increase of plasma glucose in both groups. There was a more rapid increase in blood lactate and pyruvate as well as in plasma cyclic AMP levels in the awake rats than in the anesthetized rats. By contrast, plasma glycerol levels were unaltered by bleeding, and plasma FFA levels were decreased in both groups. At the end of the 4-h bleeding period plasma glucose was higher and blood lactate levels were lower in the awake rats. The initial changes in plasma metabolite levels appeared to be directly related to changes in plasma catecholamine levels. There were no differences in the relationship between the adrenaline level and cyclic AMP or glucose increase, suggesting that anesthesia did not alter beta-adrenoceptor sensitivity, but only catecholamine concentrations. The results also indicate that awake rats tolerate long-lasting blood volume loss better than anesthetized rats, because the sympatho-adrenal activation is more short-lasting.