The effect of 2,6-diisopropylphenol on the release of adenosine triphosphate in human erythrocytes

The nucleotide adenosine triphosphate (ATP) has long been known to drive and participate in countless intracellular processes. One of these processes is ATP's ability to function as a powerful vasodilator. It has been well established that isolated healthy human erythrocytes (RBCs) release ATP when exposed to a hypoxic/hypercarbic environment. Propofol is the most common intravenously administered anesthetic in the United States and is known to cause a dose-dependent decrease in blood pressure. Differing hypotheses exist as to the exact mechanism of this drug-induced hypotension. A literature review demonstrates the variety of these hypotheses, some of which include: direct vasodilation, myocardial depression, and blunting of the baroreceptor reflex. This research study investigates the potential release of ATP from RBCs upon exposure to Propofol's active ingredient 2,6-diisopropylphenol. One mechanism of Propofol-induced hypotension may include the release of ATP from RBCs when exposed to 2,6-diisopropylphenol.;METHODS: RBCs were obtained from a donor. The RBCs were washed and then resuspended and diluted 1/1000 in Krebs-Henseleit solution. This process served to isolate the RBCs and enabled the researchers to perform manual counting. All samples were maintained at a temperature of 37° C through incubation and exposed to 2,6-diisopropylphenol for a range of 2 to 10 minutes. RBC counts were performed on each test and control group prior to testing. Test-group RBCs were then exposed to calculated doses of 2,6-diisoprophylphenol which were representative of differing plasma concentrations of Propofol. Both control and test groups were assayed using the Adenosine 5'-triphosphate Bioluminescent Assay Kit (Sigma) to determine if erythrocytes exposed to 2,6-diisopropylphenol released a greater amount of ATP than the control RBCs. Post-testing RBC counts were preformed to determine if cell lysis had occurred.;RESULTS: Results indicated a significant increase (p < 0.05) in ATP release from RBCs exposed to induction dose concentrations (50 ?g/ml) of 2,6-diisopropylphenol in vitro. The amount of ATP released in these experiments extrapolates to a physiologic concentration comparable to 10-6 M, which has previously been shown to result in maximal vasodilation. Statistical comparison of pre- and post-test RBC counts showed no significant difference (p > 0.05), thus ruling out RBC lysis as a source of the increased extracellular ATP.;CONCLUSION: The results of this research imply that an unexplored mechanism for the dose-dependent hypotension produced by the anesthetic agent propofol may exist. It was found that 2,6-diisopropylphenol, the active ingredient in propofol, significantly increases the release of ATP from human RBCs in vitro. It is possible that this increased release of ATP may result in the vasodilation and hypotension seen when propofol is administered in bolus dose concentrations, such as during anesthetic induction. Additional research including in vivo testing would be necessary to confirm this hypothesis.