Abstract
Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome. The underlying cause of this rise in noradrenaline is unknown, but a clue may be that mercury increases noradrenaline output from the adrenal medulla of experimental animals. We therefore determined the proportion of people from 2 to 104 years of age who had mercury in their adrenal medulla. Mercury was detected in paraffin sections of autopsied adrenal glands using two methods of elemental bioimaging, autometallography and laser ablation-inductively coupled plasma-mass spectrometry. Mercury first appeared in cells of the adrenal medulla in the 21–40 years group, where it was present in 52% of samples, and increased progressively in frequency in older age groups, until it was detected in 90% of samples from people aged over 80 years. In conclusion, the proportion of people having mercury in their adrenal medulla increases with aging. Mercury could alter the metabolism of catecholamines in the adrenal medulla that leads to the raised levels of plasma noradrenaline in aging. This retrospective autopsy study was not able to provide a definitive link between adrenal mercury, noradrenaline levels and hypertension, but future functional human and experimental studies could provide further evidence for these associations.
Highlights
Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome
Plasma noradrenaline increases with a ge[1], and increased noradrenaline activity is thought to play a role in the pathogenesis of essential h ypertension[2,3,4] and the metabolic syndrome[5]
The cause of this decreased adrenaline output remains unknown. Another possible origin for the elevated noradrenaline in aging is the uptake of toxic metals by the adrenal medulla
Summary
Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome. The result would be an increased output of noradrenaline and a decreased secretion of adrenaline, the situation found in human aging This mechanism provides a potential link between the findings, in both essential hypertension and the metabolic syndrome, of increased sympathetic a ctivity[4,5] and previous exposure to m ercury[17,18]. It may underlie the acutely-raised noradrenaline levels and hypertension that follow accidental exposure to mercury[14]. To see if mercury in the adrenal medulla could contribute to the changes in catecholamine levels found in aging, we looked for the presence of mercury and other toxic metals in the adrenal glands of people aged between 2 and 104 years
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