Improved method for the measurement of chicken and rat pineal serotonin N-acetyltransferase activity.

EGTA, a nonspecific ion chelator, showed very good potential for preventing the loss of serotonin N-acetyl transferase activity (arylamine: acetyl-CoA:N-acetyltransferase, EC 2.3.1.5.) (SNAT) from rat and chicken pineal glands during preincubation at 37 degrees C before substrate addition. SNAT activity was higher than that of the controls when EGTA was present in the homogenization buffer due to the prevention of the loss of activity probably not only during the preincubation period but also during incubation with its substrates. This characteristic of EGTA suggests that its use is suitable in the improved SNAT assay described in this paper since higher SNAT activities were found in both rat and chicken pineal glands than the activities recorded with the usual methods.