Adrenergic regulation of Rana balcanica erythrocyte pyruvate kinase

The regulation of pyruvate kinase activity by noradrenaline was investigate d in Rana balcanica red cells. Thirty minutes of noradrenaline incubation i nduced a significant increase in the V-o/V-max ratio of pyruvate kinase. Th e S-0.5 for phosphoenolpyruvate of the enzyme significantly increased in th e presence of noradrenaline while the K-m for ADP decreased. In response to hormonal stimulation the Na+/H+ exchange was activated as was shown by the increase in Na+ and cyclic adenosine monophosphate from the 3rd mill of in cubation. All these effects were specific to alpha(1) and beta antagonists. High concentrations of fructose diphosphate significantly activated the en zyme in the presence of noradrenaline but not in its absence. Furthermore, the presence of noradrenaline partially released the inhibition of the enzy me by adenosine triphosphate, inorganic phosphate and 2,3-diphosphoglycerat e. The results suggest that noradrenaline stimulates glycolysis through pyr uvate kinase activation. The mechanism of stimuilation may is through Na+/H + exchange activation, cyclic adenosine monophosphate concentration and Na-K+-ATPase activation.