The Activation of Pyruvate Dehydrogenase by Glucagon in Hepatocytes is Diminished by Phorbol Myristate Acetate: A role for Cytoplasmic Calcium in Dehydrogenase Regulation

  • James M. Staddon
  • Richard G. Hansford
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 232)


It is known that glucagon, vasopressin and phenylephrine each cause an increase in the active, non-phosphorylated, form of the intramitochondrial enzyme pyruvate dehydrogenase (PDHa) when added to suspensions of hepatocytes (Assimacoupolos-Jeannet et al.,1983; Oviasu & Whitton,1984). The interconversion is mediated by a specific kinase and phosphatase (see Reed,1981). The observation that the phosphatase can be activated by Ca2+ (Denton et al., 1972) has led to the proposal that the increase in PDHa content occurring in response to the hormones may be due to an increase in the mitochondrial Ca2+ content, [Ca2+]m, occurring as a consequence of an increase in the concentration of cytoplasmic free Ca2+, [Ca2+]c, (Denton & McCormack,1980). Consistent with this hypothesis is the observed increase in [Ca2+]c in hepatocytes in response to glucagon, vasopressin and phenylephrine (Charest et al.,1983; Berthon et al.,1984; Thomas et al.,1984; Sistare et al.,1985; Staddon & Hansford,1986). Further, the PDHa content of liver mitochondria can be regulated by extramitochondrial, physiological, free [Ca2+] (McCormack,1985).


Phorbol Ester Pyruvate Dehydrogenase Liver Mitochondrion Phorbol Myristate Acetate Cytoplasmic Calcium 
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Copyright information

© Plenum Press, New York 1988

Authors and Affiliations

  • James M. Staddon
    • 1
  • Richard G. Hansford
    • 1
  1. 1.National Institutes of Health National Institute on AgingGerontology Research CenterBaltimoreUSA

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