| 2,3,7,8 -Tetrachlorodibenzo - p - dioxin(TCDD) is considered the most potent congener of dioxin - like compounds. TCDD and relat-ed congeners have been shown to act as developmental and reproduc-tive toxicans. This group of toxicants decrease testicular and accessory sex organ weight, alters testicular morphology, and decreases sperm production. TCDD also decreases testicular production of testosterone and alters the regulation of pituitary luteinizing hormone secretion. In utero and lactational exposure of male rats to TCDD, whether the plas-ma androgen concentration was reduced? The statistical significance of this decrease has not yet been established due to large interanimal var-iability, dose, treatment opportunity, difference between species.EGF is a potent mitotic factor. It promotes proliferation and dif-ferentiation of epithelial and somatic cells by binding with EGFR. EGF is synthesis by submaxillary gland mainly. Besides SMG, the tis-sue sources of EGF are the epithelial cells of the renal proximal tu-bules , prostate gland, seminal vesicle and the testis. A series of re-cent observations suggests that EGF may play an important role in the male reproductive system. . Few article have address the effect of TC-DD on the synthesis of EGF and EGFR in submandibular gland. So this is one of the purposes of present research.In present report, pregnancy Sprague - Dawley rats were admin-istered a single oral dose of TCDD on Day 15 of gestation. Serum an-drogen concentration of male rat offspring in different development pe-riod was measured by RIA. The expression of AR, EGF in testis and of EGF,EGFR in submandibular gland were observed by IH method.Methods1. Four - month - old pregnant Sprague - Dawley rats were ad-ministered a single oral dose of TCDD (5ug/kg; 2ml/kg) or vehicle (corn oil/acetone 19/1 v/v) on Day 15 of gestation( Day 0, sperm positive ).On the day of birth ( PND 0) , litters were adjusted to four males and females to ensure similar lactational vehicle or TCDD exposure across litters. On PND 21, male offspring which were not sacrificed were weaned and housed independently.2. On PND 21, 32, 49, or 63, ten male offspring were eutha-nized by decapitation, and blood was collected. Blood was centrifuged for 10 min at 12000g, 4 and plasma was stored at -70. Serum androgen concentration were measured by RIA.Submandibular gland and left testis were fixed, dehydrated, as-bestos embedded. 5um sections were stained by IH.3. The relative expression of AR, EGF in testis and of EGF, EG-FR in submandibular gland were analysis by Coolspapfx Imaging Meta-Morphous System. Statistical analyses of the data were analyzed by SAS solfware, expressed by x .Results1. Body weight and testis weightBoth the body weight and testis weight of TCDD group were re-duced than control group. On PND 21, the decrease was statistically significant.2. Serum androgen concentrationTestosterone levels in control males were very low on PNDs 21 and 32but increased near twice by PND 49. Plasma androgen concen-trations showed a similar pattern in TCDD - exposed male rats but ten-ded to be lower than control at most times, although decreases were not statistically significant except PND 21(P<0. 05).3. ImmunohistochemistryOn PND21, there were not AR positive reaction production in testis Ley dig cells. Germinal epithelia of control showed AR positive immunoreaction, stained stronger than TCDD group. The different was statistically significant( P <0. 01). On PND32, both Leydig cell and germinal epithelia showed AR positive immunorection. , but no differ-ence.On PND32, 49, there were statistically significant on testis EGF reaction production..On PND32,49, TCDD promoted the expression of EGF and EG-FR in submandiibular gland of TCDD group.On PND21, 32, there were not significant difference.DiscussionTCDD s action like hormone or anti - hormone. It could disturb endocrine balance. Amount of researches showed TCDD can adversely affect the male reproductive sy... |
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