Serum
copper levels must be maintained between very strict limits for the maintenance of good health. High levels have recently been linked to
Alzheimer's disease while low levels during pregnancy cause
enzootic ataxia (
swayback disease) in offspring. In this study, we investigated the prolonged effect of serum
copper that was maintained at and around 0.5 ppm, the level presently regarded as safe. Pregnant sheep and rabbits in the last trimester (1-4 weeks) of pregnancy were treated with the
copper chelator ammonium tetrathiomolybdate (ATM). Treatment was continued until the young were one month old at which time the animals were sacrificed Serum
copper levels of the parents and offspring were monitored by atomic absorption. The difference spectra (400-630 nm) was examined and SDS PAGE was used to evaluate the
protein composition of the brain mitochondria. The anatomy of the midbrain was also studied. Although the young sheep and rabbits from the ATM-treated mothers showed no visible signs of disability or
swayback disease, the midbrain of those young animals with serum
copper between 0.3-0.9 ppm showed evidence of vacuolation, cavitation and chromatolysis. In contrast, the difference spectra and the
protein composition of the brain mitochondria from these animals were all normal. These results suggest that although animals may appear normal and exhibit some normal
biochemical markers, serum
copper in the region of 0.5 ppm may not be safe for some breeds of sheep or rabbits. It is possible that a similar situation applies to man.