Previous studies have shown that red blood cell (RBC) concentrations of adenine 5'-triphosphate (ATP) may be a key factor for post exercise effects responsible for cardiovascular protection. To test this concept further, we investigated the effect of isoproterenol on ATP metabolism in RBC using a freely moving rat model in vivo. Sprague Dawley rats were given either isoproterenol (30 mg/kg) or saline by subcutaneous (sc) injection. Blood samples were collected sequentially for up to 6 hours for measurement of adenine nucleotides in the RBC. Hemodynamic recordings were collected throughout the experiment. We have found isoproterenol induced 50% mortality under the experimental condition. It decreased systolic blood pressure (SBP) and diastolic blood pressure (DBP) immediately after the injection by -64 ± 22 and -64 ± 20 mmHg in less than 15 min, and increased HR steadily by +158 ± 59 bpm at the end of the experiment. Isoproterenol also increased RBC concentrations of adenine 5'-monophosphate (AMP) from 0.04 ± 0.01 to 0.28 ± 0.23 mM (+500%). The rats died had much greater breakdown of ATP to adenosine 5'-monophosphate (AMP) in the RBC than those surviving from the injury (p<0.05 for all the comparison).

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