Urinary homovanillic acid and serum prolactin levels in children with low environmental exposure to lead

Abstract

Current evidence suggests that the neurotoxic effects of lead may partially be mediated through interference with the dopaminergic system. The aim of this study was to assess the levels of two peripheral dopaminergic markers--serum prolactin (Pro-S) and urinary homovanillic acid (HVA-U)--in children living around two lead smelters, who are presumed to be exposed to high environmental lead pollution (n = 200), and compare their results with 200 age- and sex-matched controls living in an area unpolluted by heavy metals, giving a total of 400 children (200 boys and 200 girls). The influence of lead exposure on HVA-U and Pro-S was assessed by stepwise multiple regression, testing lead concentrations in blood (Pb-B), age, sex and area of residence as predictors. Though lead levels were significantly higher in boys and in the lead-polluted environment, mean Pb-B values were relatively low, indicating a low uptake of lead in the contaminated environment (39.5 micrograms l-1, range 4.6-165 micrograms l-1, n = 200), and no significant correlation could be found with either Pro-S or HVA-U. However, when the subgroup of 121 children with Pb-B levels above 50 micrograms l-1 were considered, a weak positive correlation was found between Pb-B and HVA-U (r2 = 0.04, p = 0.03), whilst in the even smaller subgroup of 15 children with Pb-B levels above 100 micrograms l-1, Pro-S appeared to be positively correlated with Pb-B, though the numbers of children were too small for the correlation to reach statistical significance (p = 0.095). These weak associations, probably not important in biological terms, indicate that Pro-S and HVA-U are not useful biomarkers at present exposure levels to lead in the environment. Nevertheless, the finding of subtle biochemical alterations in the dopaminergic system at Pb-B levels of around 100 micrograms l-1 supports the recommended setting of the action level at this value.

Blood lead, cadmium and mercury among children from urban, industrial and rural areas of Fez Boulemane Region (Morocco): Relevant factors and early renal effects

“…This finding is in agreement with some previous studies reporting that boys tend to have a higher uptake of environmental heavy metals than girls, principally due to behavioral differences [68]. Another factor that can explain this difference related to gender is shown in Table 4; as the BCLs in children increase with the increasing number of cigarettes smoked at home.…”

The influence of chronic and subacute exposure to lead on the levels of prolactin, leptin, osteopontin, and follistatin in humans

“…Analogical results were obtained in a group of 101 pregnant women, 13 while no significant association between prolactin and lead levels was found in 400 children environmentally exposed to lead. 10 However, Govoni et al 14 showed higher level of prolactin in a group of male workers occupationally exposed to lead with blood lead levels higher than 40 µd/dl than in those with blood lead level below this value. Similarly, Lucchini et al 15 found higher prolactin level in a group of 66 lead-exposed workers with mean blood lead level 27.50 ± 28 µg/dl than in an unexposed control group with mean blood lead level of 8.11 ± 4.47 µg/dl.…”

“…Therefore, a biphasic dose-dependent effect of lead on the dopaminergic neurotransmission has been postulated as well. 10 An existence of such mechanism may explain also discordant results of studies on prolactinemia in lead exposure. In the present study, prolactin level was significantly lower in workers chronically exposed to lead than in the control group, while a short-term exposure to lead did not significantly affect its level.…”

Weekly Biological Variability of Urinary Organic Acids

“…Concentrations of organic acids in urine have been measured for diagnosis of inborn errors of metabolism and as markers of essential nutrient status, neurotransmitter disturbances, toxicant effects and small intestinal microbial overgrowth. [1][2][3][4][5][6][7][8] Elevations of specific organic acids have been reported as markers of nutritional deficiencies, including xanthurenic acid (vitamin B 6 ), 9 formiminoglutamic acid (folic acid), 10 and 3-hydroxyisovaleric acid (biotin). 11 Neurotransmitter metabolites in urine have been found useful in studies of cancer 12 and behavioral disorders, 13 and exposure to xenobiotic compounds has been monitored by measuring excreted metabolic products.…”

“…14 Rationales for using organic acids as markers of various disorders have been reviewed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Variability of urinary analytes has been the subject of multiple reports. [16][17][18][19] When 10 overnight urine samples were collected by 10 patients with non-insulin-dependent diabetes mellitus, urinary albumin excretion showed total variability of 12%.…”