Effects of diazinon on nucleotide and amino acid contents of chick embryos. Teratogenic considerations.

The effects of diazinon (DZN), an organophosphorus (OP) insecticide, and nicotinamide (Nam) on the pyridine nucleotide, purine and pyrimidine ribonucleotides, and free alpha amino acid contents of chick embryos were determined. The teratogen (DZN) and/or the anti-teratogen (Nam) were administered by the intravitelline route to chicken eggs at day 3 of incubation, and nucleotide and amino acid analyses were made on acid-soluble extracts of homogenates of the embryos at day 10. The results show that the amounts of both the oxidized and reduced forms of NAD and NADP were decreased by the insecticide and restored by Nam. The amounts of the purine and pyrimidine ribonucleotides in the embryos were also decreased by DZN but their changes were proportionately not as great as those of the pyridine nucleotides. The levels of the purine and pyrimidine ribonucleotides were also wholly or partially restored by Nam. Neither DZN nor Nam had any effect on the "energy charge" of the embryos. The levels of free tryptophan (TRP) and histidine (HIS) were decreased by DZN while the levels of threonine (THR) and aspartic acid (ASP) were increased. All other amino acid levels remained virtually unchanged in response to DZN or Nam. Based upon these findings, a possible involvement of TRP in OP insecticide-induced micromelia, parrot beak, and abnormal feathering in chick embryos is considered.