Tyramine in the assessment of regional adrenergic function


  • F. Adams
  • M. Boschmann
  • K. Schaller
  • G. Franke
  • K. Gorzelniak
  • J. Janke
  • S. Klaus
  • F.C. Luft
  • M. Heer
  • J. Jordan


  • Biochemical Pharmacology


  • Biochem Pharmacol 72 (12): 1724-1729


  • Regional adrenergic function is difficult to assess in humans. Tyramine given through a microdialysis probe may be a useful tool in this regard. However, tyramine data is hard to interpret given the drug's complex mode of action. We characterized the response to tyramine, isoproterenol, and dopamine in adipose tissue with microdialysis probes in normal subjects. We measured glycerol concentrations to follow changes in lipolysis and monitored tissue perfusion with ethanol dilution. During perfusion with tyramine, dialysate glycerol concentration increased dose-dependently from 83+/-8muM at baseline to 181+/-18muM at 3.5mM tyramine (p<0.001) followed by a fall down to 121+/-9muM at 35mM tyramine (p<0.001). Propranolol almost completely blocked this response. A similar lipolytic response was not observed in isolated human adipocytes. Dopamine <35muM did not replicate the tyramine-induced lipolysis; however, dopamine >35muM potently inhibited lipolysis. We conclude that tyramine-induced lipolysis is explained by a pre-synaptic mechanism. Tyramine applied through a microdialysis probe in concentrations up to 3.5mM can be used to assess pre- and post-synaptic mechanisms regulating lipid mobilization.