الفهرس 
INTRODUCTION AND AIM OF THE WORK
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Abstract
An increase in the human population, industrial pollution and heavy road traffic are believed to be responsible for the increased release of lead into the environment. Lead exposure can cause adverse effects on many organs in the body leading to neurological disorders, cognitive impairment, anemia, hypertension and renal disorders. Also, it has adverse effects on both male and female reproductive systems.
Lead exposure suppressed the hypothalamic-pituitary-testicular axis, thus altered the morphology of spermatozoa and the relationship of cell types in the testes. In females, lead accumulation in the ovary causes dysfunction of folliculogenesis resulting in decreased fertility, less ability to sustain pregnancy and low pregnancy outcomes. Acute exposure to high levels of lead could result in stillbirth or miscarriage. Chronic low lead level exposure is associated with low birth weight and pre-term delivery.
Antioxidant may play an important role in abating some hazardous effects of lead. Vitamin E is known as the anti-sterility vitamin because it is found to be necessary for normal reproduction as well as it acts as low molecular antioxidant that scavenges free radicals.
This Experimental study aimed to:
1- Investigate the effect of chronic i.p. lead administration for 6 weeks on plasma levels of LH, FSH in male and female rats and testosterone in male and estradiol and progesterone in female.
2- Study the possible mechanisms of lead toxicity by measuring plasma levels of MDA and TAC as markers of OS and caspase 3 as a marker of apoptosis.
3- Study the effect of oral administration of vitamin E for 6 weeks on the changes occurring in rat model of chronic lead toxicity.
4- Study the histolopathological changes in the anterior lobe of the pituitary gland and the gonads occurring after chronic lead administration as well as after treatment with vitamin E.
One hundred and four adult Wistar Albino rats (52 males and 52 females), initially weighing 180-200 gram and initial age range from 8-10 weeks. Rats were randomly divided into the following 4 groups:
1. Group I (normal control group): It consisted of 24 rats. Of them (12 males and 12 females), 12 rats received olive oil orally (vehicle of vitamin E), 12 rats received DW, vehicle of lead) i.p. in the same volume as lead exposed groups. The animals were sacrificed after 6 weeks.
2. Group II: It consisted of 40 rats (20 males and 20 females). This group was subdivided into 2 subgroups:
Group IIa (Lead exposed group): It consisted of 20 rats (10 males and 10 females) injected with lead acetate (10 mg/kg/day 5 times/week, i.p. for 6 weeks) purchased from Al-Nasr pharmaceutical chemicals company, Egypt) and dissolved in distilled water. The animals were sacrificed after 6 weeks.
Group IIb (Lead withdrawal group): It consisted of 20 rats (10 males and 10 females) injected with lead acetate (10 mg/kg/day 5 times/week, i.p. for 6 weeks). The animals were sacrificed 6 weeks after stoppage of lead injection.
3. Group III (Lead then vitamin E treated group): It consisted of 20 rats (10 males and 10 females) injected with lead acetate (10 mg/kg/day 5 times/week, i.p. for 6 weeks) followed by oral administration of vitamin E by stomach tube (50 mg/kg/day 5 times/week for another 6 weeks (purchased from Sigma-aldrich chemical company and dissolved in olive oil). The animals were sacrificed after 12 weeks.
4. Group IV (Lead with vitamin E treated group): It consisted of 20 rats (10 males and 10 females) received oral vitamin E by stomach tube (50 mg/kg/day 5 times/week for 6 weeks) simultaneously with lead acetate (10 mg/kg/day 5 times/week, i.p. for 6 weeks). The animals were sacrificed after 6 weeks.
Immediately at the end of the experiments, rats were sacrificed by cervical dislocation. Blood samples were collected from retroorbital venous plexus to measure LH, FSH, testosterone, estradiol, progesterone, TAC, MDA and caspase 3. The pituitary glands, testes and ovaries were dissected and processed for histological examination.
Results of the present study showed that lead exposure decreased the plasma levels of LH and FSH in both male and female rats and decreased testosterone level in male rats and decreased estradiol and progesterone levels in female rats compared to control group. This was supported by the results of the histological examination of the anterior pituitary gland and the gonads. Electron microscopic examination of the gonadotrophic cells of the anterior pituitary showed that the cells were altered in their shape, Golgi system and ribosomes (grouped in synthesis centers) were less represented, The cytoplasm showed extensive vacuolations. The number of hormone secreting granules was highly decreased in the majority of cells. Light and EM examination of the testis showed sever degeneration and disruption of overall integrity of the seminiferous tubules. Many tubules revealed multiple vacuolations and the spermatogonia appeared dissociated from each other. Sertoli and Leydig cells ultrastructure showed the nuclei with greatly distorted irregular outlines. The chromatin revealed central and peripheral condensations. The cytoplasm appeared greatly disrupted, vacuolated and devoid of the organelles apart from few swollen and destructed mitochondria, ribosomes, rough endoplasmic reticulum, lipid droplets and lysosymes. Examination of the ovary revealed damage and decreased number of primordial, primary, preantral and graffian follicles while the number of atretic follicles was increased. The graffian follicle lost its original shape, oocytes appeared degenerated, granulosa cells were reduced in number, scattered with vacuolated cytoplasm and appeared dissociated from theca cells.
Withdrawal of lead in both male and female rats resulted in partial improvement in all biochemical and hormonal parameters measured but the significant improvement occurred in rats given vitamin E either after or with lead. The improvement appeared in the form of increased the plasma levels of LH, FSH, testosterone, estradiol and progesterone and TAC and decreased MDA and caspase 3 levels compared to lead adminstration group. Electron microscopic examination of gonadotrophic cells of the anterior pituitary showed numerous hormone secretion granules, numerous well-developed Golgi bodies and mitochondria disposed in the cytoplasm. Regarding the testis, the majority of seminiferous tubules showed nearly normal architecture with the appearance of the different types of germ cells. The Sertoli cells, primary spermatocyte, spermatid, Leydig cells revealed marked recovery from damaging effect of lead. The ovary showed increased numbers of primary, primordial follicles in comparison to lead exposed group and reduction in the number of atretic follicles. Graffian follicle, granuolosa and theca cells were normal in shape.
In conclusion, the results of this experimental study demonstrated the following:
1) Chronic lead administration resulted in gonadal dysfunction in both male and female rats through dual effect:
a) Central effect on the pituitary gonadal axis manifested by significant decreased plasma levels of FSH, LH, and degeneration of gonadotroph cells of anterior pituitary gland detected by electron microscopic examination,
b) Direct effect on testis and ovary manifested by decreased plasma levels of testosterone, estradiol, progesterone and marked alterations in the structure of testis and ovary detected by light and electron microscopic examinations that appeared in the form of degeneration of seminiferous tubules, Sertoli and Leydig cells, atrophy and decreased number of ovarian follicles plus degenerated oocytes and apoptosis of granulosa cells.
2) Lead acetate induced alteration in the pituitary gland and the structure and function of the gonads by induction of OS and apoptosis which was evidenced by marked increase in the plasma levels of MDA, caspase 3 and decreased level of TAC.
3) Stoppage of lead administration for 6 weeks resulted in partial improvement both at the hormonal level and in the structure of the anterior pituitary gland and gonads.
4) Supplementation of vitamin E produced marked recovery from the damaging effect of lead which is manifested by increased plasma levels of FSH, LH, testosterone, estradiol and progesterone as well as improvement in histologopathological structure of anterior pituitary gland, testis and ovary. The recovery appeared with administration of vitamin E after lead and reached the maximum improvement in rats given vitamin E with lead.
5) Moreover, supplementation of vitamin E with or after lead has anti-oxidant activity and anti-apoptotic effect which is evidenced by decreased plasma levels of MDA, caspase 3 and increased level of TAC.
Therefore, the present findings demonstrated that vitamin E, through its antioxidant and anti-apoptotic activity, has a protective and therapeutic effect on gonadal dysfunction-induced by lead through stimulating the proliferation of gonadotrophic cells of the anterior pituitary gland and increasing the number of hormone secreting granules inside them as well as restoration of normal histological structure of testis and ovary.