The effect of dietary zinc deficiency on the mossy fiber zinc content of the rat hippocampus

Abstract

The effect of dietary zinc deficiency on the mossy fiber zinc content of the rat hippocampus was investigated using PIXE (Particle Induced X-Ray Emission) spectroscopy. Using the proton microbeam (60 X 60 microns), 2 mm line-scans were made on hippocampal sections and the data were expressed as absolute zinc concentrations. Values of 55 and 136 ppm (dry weight) were found for the mean background zinc level and the maximum mossy fiber zinc level, respectively, in animals fed a control diet containing 50 ppm zinc. Treatment of these animals with dithizone caused about 50% reduction in the maximum mossy fiber zinc level. Feeding a zinc-deficient diet for 28 days did not cause a decrease in the mossy fiber zinc level, however, feeding the zinc-deficient diet for 90 days reduced the maximum mossy fiber zinc level by about 30%. The results are discussed in relation to the behavioral abnormalities that have been observed in zinc-deficient animals.

Deficiencies of Hippocampal Zn and ZnT3 Accelerate Brain Aging of Rat

“…It is generally accepted that Zn is highly concentrated in synaptic vesicles in the giant boutons of hippocampal mossy fiber terminals which exists as a chelatable form (4,5) and released with glutamate upon physiological stimulation (6 -8). Since it has been confirmed that chelatable Zn level in the mossy fiber terminals was about 20% of total Zn level in the hippocampus (33), it is likely that the reduction in the hippocampal Zn level in aged SAMP10 mainly reflected a decrease in chelatable Zn in the hippocampal mossy fiber terminals (16,17,34).…”

Perinatal Hypothyroidism Decreases Hippocampal Mossy Fiber Zinc Density in Rats

“…First, the serum zinc deficit may not have been of sufficient magnitude to affect mossy fiber zinc density. Wensink et al [20] examined the effects of zinc-deficient diets on mossy fiber zinc measured by particle-induced X-ray emission analysis in mature rats. Consumption of a zinc-deficient diet for I month decreased serum zinc con centration to one third of control serum zinc values.…”

“…It has been estimated that histochemically detectable mossy fiber zinc accounts for 8-15% of total hippocampal zinc [18][19][20]. Given the impact of perinatal hypothyroidism on hippo campal kainate receptors and the similar anatomical loca tion of these kainate receptors and mossy fiber zinc, we hypothesized that perinatal PTU treatment causes hippo campal mossy fiber zinc deficits.…”

Effect of the zinc chelator N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) on hippocampal mossy fiber calcium signals and on synaptic transmission

“…The difference between the environments of action, intra-or extracellular, for membrane-permeant and impermeant chelators, respectively, containing different zinc-binding ligands (Frederickson et al, 2000), also may contribute to the observed differences. For example, it has been shown that zinc-deficient diets lead to 30% reduction in mossy fiber zinc (Wensink et al, 1987). Furthermore, it has been reported that, in in vivo studies, TPEN can prevent zinc and iron neurotoxicities but not copper toxicity, in spite of the fact that it has a much higher affinity for copper (10 20 M -1 ) than for zinc (10 15 M -1 ) (Armstrong et al, 2001).…”