1Department of Biochemistry & Biophysics, St. John’s National Academy of Health Sciences
2Department of Neurophysiology, National Institute of Mental Health & Neurosciences, Bangalore
Lead is found in small but appreciable quantities in air, soil, drinking water, and food. Exposure to such amounts of lead does not cause acute lead toxicity, but produces subtle effects, particularly in children. The CDC, USA advocates “safe” or “acceptable” levels of blood lead up to 10mcg/dl, while osha declares blood lead levels up to 40mcg/dl as “safe” or “acceptable” in the occupationally exposed. The objective of this study was to see if blood levels considered “safe” can cause damage to the developing brain producing neurochemical, neurobehavioral, and morphological defects.
Albino wistar rats were used, which were divided into control and lead-treated groups. The control group was given unleaded water, while the lead-treated group was given 50ppm lead acetate in drinking water. Both these groups were maintained for 45 days. On day 45, the experimental animals were weighed, subjected to a passive avoidance test to assess their neurobehavioral faculty, and their blood analysed for ZPP and lead. They were then sacrificed and the following neurotransmitters: norepinephrine, dopamine, and serotonin, together with their metabolites (mhpg, dopac and 5-hiaa respectively), were estimated in three brain areas - frontal cortex, hippocampus, and striatum by HPLC-ECD. Sections from these areas were also sent for histopathology.
It was found that blood lead, ZPP, norepinephrine, serotonin, mhpg, and 5-hiaa were increased, while dopamine and dopac were decreased generally. Passive avoidance test showed memory and learning deficits. Histopathology revealed extracellular oedema and pas+ve stained granules in the perivascular astrocytes.
This study shows that even “safe” or “acceptable” blood lead levels produce neurochemical, neurobehavioral, and morphological alterations.
