Regulation of Hormonal Induction of Chick Liver Cytosol-Specific Phosphoenolpyruvate Carboxykinase

Abstract

Administration of glucagon, epinephrine, or dibutyryl cAMP to chicks induced cytosol-specific phosphoenolpyruvate carboxykinase in liver. In vitro translation assay with poly(A)⁺RNA indicated that this induction was due to the increase in phosphoenolpyruvate carboxykinase-coding mRNA synthesis which resulted from an increased level of hepatic cAMP. Either hydrocortisone or α-adrenergic agonist was ineffective for the induction by itself, but showed a significant effect when administered together with one of the inducing agents given above. In particular, hydrocortisone enhanced the synthesis of phosphoenol-pyruvate carboxykinase-specific mRNA without changing the profile of the time courses of the induction and of hepatic cAMP level. Those observations suggest that the fundamental machinery required for induction of cytosol-specific phosphoenolpyruvate carboxykinase in liver is shared in common between rat and chick, and that the absence of appreciable induction of cytosol-specific hepatic phosphoenolpyruvate carboxykinase in starved chicks is due to neither lack nor impairment of the hormone-mediated induction mecha-nism, but is due to the difference in usage of the genetic information between the two animal species.