Study On The Chronic Effects Of Cadmium Chloride On The Male Reproductive System Of Adult Rats Exposed Orally And Its Repression Effects

ObjectiveThe present study was to establish the adult rat model exposing cadmium chloride orally, to investigate the chronic effects of cadmium chloride on the testis, epididymis and sperm of adult rat, and to assess the repression time-effects of the method of natural recovery and zinc ion drug treatment. The purpose was to evaluate the male reproductive tract damage of chronic oral overtaking cadmium ion, to provide the etiologic evidence of male infertility related to the cadmium ion polution, and to define the therapeutic result of the treatment plan.Materials and MethodsSeventy-two SD rats (approximately 200g each), aged 10 weeks, were randomly divided into twelve groups. They were fed diet containing Cd²⁺ 0 mg/kg, 8 mg/kg, 40 mg/kg, 200 mg/kg for one (group A, B, C, D), two (group E, F, G, H) and four (group I, J, K, L) months, respectively. Each rat had 100 g/(kg BW · d) of diet. After treatment, the histological and microstructural changes of testis, epididymis and sperm, the nuclear maturation changes of sperm and the epididymal sperm parameters were examined to evaluate the effect of cadmium chloride. In the repression experiment, the group O rats were fed with diet containing Cd²⁺ 200 mg/kg for 2 months and the normal diet for subsequent 2 months. The group M and N were fed with diet containing Cd²⁺ 200 mg/kg for 2 months and diet containing Zn²⁺ 100 mg/kg or 500 mg/kg respectively for subsequent 2 months. The group H and I were set as the positive and negative control group respectively. After that, the testicular and epididymal parameters were measured.Results1. Histological studies revealed that the layer of primary spermatocyte of group D, H and L was separated from the layer of spermatogonium, and then sloughed into the lumen. With transmission electron microscope, the Sertoli cell of group D had the cytoplasmic vacuoles, electron-lucent cytoplasm and residual bodies. Moreover, there were more secondary lysosomes, lipid droplets, residual bodies and loop shape mitochondria in group H than those in group E, so as in group L than those in group I. Testis coefficient of group H and L were increased than group E and I(P<0.01). The daily sperm productions were lower when compared between group D and group A (P<0.05), group G, H and group E (P<0.01), besides group K, L and group I (P<0.01). The daily sperm productions showed the significant negative relationship to dose (P<0.001).2. Histological studies revealed that the epididymal epithelium cells had been swollen, and vacuolar cytoplasm, besides the nuclear deformed. The degeneration aggravated when the doses were increased. With transmission electron microscope, in caput epididymis the stereocillia of principal cell from group J decreased, vacuoles appeared in the cytoplasm. The stereocillia of group K shortened, while numerous lysosomes, multivesicular bodies and lamellar bodies appeared in cytoplasm. In group L, the principal cell showed pyknosis, dilated and disorganized Golgi apparatus, sparse stereocillia. In corpus epididymis, the number of lysosomes, multivesicular bodies, and swollen mitochondria increased in group J. And in group K the secretory vesicles and dilated Golgi apparatus increased. Furthermore, the Golgi apparatus disorganized in group L, the tight junctions between the principal cells disappeared. In cauda epididymis, the principal cell from group J showed pyknosis, mitochondria increased and deformed. In group K the Golgi apparatus disorganized and the mitochondria swollen. The principal cell and basic cell showed apoptosis in group L.3. The cauda epididymal sperm counts, sperm viability, sperm motility and normal sperm morphology decreased between group D and group A (P<0.05), betweengroup G, H and group E (P<0.01), besides group K, Land group I (P<0.01). While the sperm deformity indices were higher in those groups. The cauda epididymal sperm counts showed the significant negative relationship to dose (P<0.00l). Meanwhile, the red AO fluorescence sperm rate of group H and L ascended significantly comparing with that of group E and I (P<0.01). Besides, the partial deletions of outer dense fibers and outer microtubules in the midpiece of sperm tail were determined in group H and L.4. Histological studies revealed that the damages of testes were gradually released from group O, M to N. The testis index in group O, M, N was still highter than group I. The daily sperm productions and cauda epididymal sperm counts were increased in group O, M, N comparing with group H. In group O, M, N, the normal sperm morphology and sperm deformity indices were improved than those of group H. However, the red AO fluorescence sperm rate of group O, M, N were still highter than that of group I.Conclusions1. Chronic dietary exposure of middle and high dose cadmium ion could damage the testis spermatogenetic epithelium and the testis function of spermatogenesis of adult rat. The toxic damage was in dose-dependent.2. Chronic oral exposure of low, middle and high dose cadmium ion could injury the caput, corpus and cauda epididymal epithelium of adult rat. The toxic damage was in a dose-dependent manner.3. Chronic dietary exposure of cadmium ion could affect the counts and morphology of cauda epididymal sperm of adult rat with low, middle and high dose. Besides, the high dose cadmium ion could effect the microstructure of sperm tail and the function of epididymis of sperm nuclear maturation.4. The chronic damage of cadmium ion on rat testis and epididymis is reversible. The progress of natural recovery is slower, comparing it treated with low Zn2+ dose. Repressed with high Zn2+ dose, it can recover to the situation as without damage.