Synthesis of homoagmatine and GC-MS analysis of tissue homoagmatine and agmatine: evidence that homoagmatine but not agmatine is a metabolite of pharmacological L-homoarginine in the anesthetized rat.

Low L-homoarginine (hArg) concentrations in human blood and urine are associated with renal and cardiovascular morbidity and mortality, yet the underlying mechanisms and the biological activities of hArg are elusive. In humans and rats, hArg is metabolized to L-lysine. The aim of the present work was to study hArg metabolism to agmatine (Agm) and homoagmatine (hAgm) in the anesthetized rat. Using a newly developed and validated GC-MS method and a newly synthesized and structurally characterized hAgm we investigated the metabolism of i.p. administered hArg (0, 20, 220, 440 mg/kg) to hAgm and Agm in lung, kidney, liver and heart in anesthetized rats. Our study provides unequivocal evidence that hArg is metabolized to hAgm but not to Agm. Whether hAgm derived from hArg's metabolism may contribute to the pathophysiological significance of endogenous hArg and for the favoured effects of pharmacological hArg remains to be demonstrated. The biology of hArg warrants further investigations.