Histamine contamination of pokeweed mitogen

The histamine content of commercial preparations of pokeweed mitogen was measured by amino acid analysis technique, automated fluorometry, and bioassay employing the guinea pig ileum. Ten samples from 5 companies were examined and found to contain between 0.026 micrograms and 167.5 micrograms of histamine per ml of solution. The protein content of 9 of these putative 5 mg samples measured by folin assay and by amino acid analysis varied from 0.56 to 4.4 mg. Their amino acid compositions were similar, except for notable variations in 3 of the 16 residues quantitated.