Complete absence of creatine but unaltered ATP levels in hearts from AGAT knockout mice

Introduction: The role of the creatine kinase (CK)/phosphocreatine (PCr) system in heart remains unclear. We created mice lacking the enzyme l-arginine:glycine amidinotransferase (AGATko), which cannot synthesize creatine (Cr) and do not accumulate a Cr precursor. Methods: Isolated hearts were subjected to 31P MRS before Cr and ATP content (HPLC) and CK activity (spectrophotometry) w ere determined. Results: AGATko hearts had no detectable (P)Cr, unaltered ATP levels, increased inorganic phosphate (Pi) and normal ex vivo contractile function.