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Abstract
Summary and conclusion
The main route for metal excretion is the urinary system. Lead is one of the most common toxic metals present in our environment. Children run a higher risk than adults at lead exposure level found in the environment. So, our study was performed aiming to clarify the histological alterations that may occur in renal tissue of young and adult albino rats due to lead exposure and to study the possible protective role of ascorbic acid against these alterations.
Thirty albino rats were utilized in this study. They were classified into three groups, 10 animals each. Group A (control), Group B (lead treated) and Group C (treated with ascorbic acid simultaneously with lead). Each group was further subdivided into two age subgroups, 5 animals each. Subgroup 1 (adult) and subgroup 2 (young).The animals were anaesthetized by ether inhalation and their kidneys were removed immediately and processed for light and electron microscopes examination.
Examination of the control group revealed that the kidneys of young animals appeared relatively smaller in size and with narrow subcapsular tubular zone comparing with control adult ones. The inner and outer medullary zones couldn’t be distinguished from each other. The superficial cortical glomeruli of young kidney appeared less mature than deeper juxtamedullary ones. The immature corpuscles appeared as small spherical structure with narrow Bowman’s space. Their podocytes were crowded and contained more diffuse cytoskeleton instead their localization under the plasmalemma of the primary processes in adult ones. The glomerular basement membrane appeared pentalaminar instead trilaminar in adult glomeruli. Also, apoptotic nuclei were detected among tubular and glomerular cells. The cells lining the convoluted tubule appeared with rounded mitochondria of scattered distribution rather than elongated basal ones of adult group. The thin limbs of the loop of Henle of renal medulla of young animals were detected with cuboidal lining cells instead simple squamous of adult ones with presence of some apoptotic nuclei.
In the adult lead treated animals, examination of renal cortex revealed more acidophilic subcapsular tubular zone and the cortical tubules and renal corpuscles appeared with irregular outlines. The renal tubular cells rested on thickened basement membranes and some of their nuclei were irregular contained more hetrochromatin. Their cytoplasm contained rounded mitochondria with less electron dense matrix and lost their basal orientation compared with that of control ones. Also, numerous lysosomes were also detected. Mesangial expansion, some apoptotic nuclei were observed within the renal glomeruli. The examination of the renal medulla revealed preservation of all medullary structures.
Examination of the kidneys of lead treated young animals revealed pale stained cortical tubules and all the glomeruli taken the immature form. The tubular lining cells appeared with electron lucent cytoplasm and rounded scattered mitochondria with destructed crestae. Swelling of endothelium, decreased fenestrations and apoptotic nuclei were observed within the renal glomeruli. However, the medullary structures were preserved.
With ascorbic acid administration simultaneously with lead, the renal structures of adult rats were preserved except few renal tubules were lined with apoptotic cells. Few cytoplasmic vacuolations were detected within the cytoplasm of some tubules. Few areas of fusion of podocytes foot processes were detected in renal glomeruli. Examination of young animals received ascorbic acid simultaneously with lead revealed preserved renal structures except few shrunken glomeruli with wide Bowman’s space. Some tubular lining cells contained vacuolations and electron dense bodies. Few vacuolated mesangial cells were also detected.
The results were discussed and we concluded that exposure to lead causes alterations in the histological structure of renal cortical tubules and glomeruli of both adult and young rats. However, these alterations take a more severe form in young rats. That may be due to the more vulnerability of the developing kidney, which complete its differentiation postnatal, to the toxic insult of the lead. So, strict precautions must be taken to prevent water and food contamination with lead especially for newborn and children. Also, lead as a causative factor of renal pathology must be considered in mind by clinicians seeking to detect the causes of renal dysfunction.
Ascorbic acid (vitamin C) supplementation could protect the kidneys from the histological alterations, induced by lead, through its antioxidant effect against lead oxidative stress. However the young kidneys were less protected by the vitamin C supplementation. So, as it is difficult to live in lead free environment, especially with children because of their exploratory behavior and frequent hand to mouth activity, we recommended improving the health of the population, especially children and the lactating mothers, through the diets balanced for nutrients without excesses especially ascorbic acid supplementation that may provide an economical and convenient method protecting the renal tissues from damage by oxidative stress.