Modified microassay for the rapid and sensitive determination of choline acetyltransferase activity using (3H)-acetyl-CoA and Fonnum's extraction.

A modified procedure for the quantitative estimation of choline acetyltransferase activity in brain tissue based upon the formation of [3H]-ACh from [3H]-acetyl-CoA is described. The labelled ACh is isolated by a modification of Fonnum's procedure using sodium tetraphenyl borate in ketonic solution. The ChAc-activity is independent on the specific activity of the [3H]-acetyl-CoA used. The substrate blank is higher than with [14C]-labelled substrate but highly stable and reproducible. The method permits the determination of ChAc activity in less than 5 mug of brain tissue. 30-40 samples may be handled by one person per hour easily.