Chick brain hypomyelination produced by 2,4-dichlorophenoxyacetic butyl ester treatment.

Fertilized hens' eggs were externally treated with 2,4-dichlorophenoxyacetic (2,4-D) butyl ester (2.4 mg/egg) before starting incubation. The specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) was diminished in the whole brain of animals born from treated eggs, as compared with controls. Myelin was isolated by ultracentrifugation from the central nervous system. Treatment with 2,4-D butyl ester produced a 65% reduction. There were no statistically significant differences in myelin phospholipids, cerebrosides, sulphatides and gangliosides between control and treated animals. Cholesterol was diminished by 12% in the treated group, while cholesterol esters were not detectable in either myelin fraction. Total myelin proteins were also decreased by 40%, without variations in their pattern. There were changes in the following ratios in the myelin of the treated group: lipid/protein, cholesterol/phospholipids, cholesterol/protein, phospholipids/protein. Collectively these findings indicate that 2,4-D butyl ester produced hypomyelination.