Stability, blood partition, and protein binding of a chemoprotective agent, 2-(allylthio)pyrazine

The stability of 2-AP, a chemoprotective agent, in various pH solutions and human gastric juice, the blood partition of 2-AP between plasma and blood cells, and the factors influencing the binding of 2-AP to 4% human serum albumin (HSA) were evaluated. 2-AP was stable in human gastric juice and pH solutions ranging from 1 to 12, however, 2-AP was unstable in pH 13 solution; the disappearance rate constant was 0.00759/h. 2-AP reached equilibrium rapidly between plasma and blood cells of rabbit blood. The equilibrium plasma/blood cells partition ratios were independent of initial rabbit blood concentrations of 2-AP, 1, 5, and 10 micrograms/ml; the values were in the range of 5.99-11.8. Binding of 2-AP to 4% HSA was dependent on HSA concentration, incubation temperature, 'the buffer' pH, and addition of acetylsalicylic acid. The binding of 2-AP was independent of buffers containing various concentrations of chloride ion, heparin, and alpha-1-acid glycoprotein.