Effects Of Oxidative Stress, Expressive Change Of Transforming Growth Factor-β₁ And Nestin In Renal Damnification In Hyperthyroidism Rats

Objective: To study the changes of anti-oxidant enzyme activities(catalase,CAT; glutathione peroxidase,GSH-Px; superoxide dismutase,SOD) and lipid peroxide (MDA) level by chromatometry as oxidantive stress index in renal cortex of hyperthyroidism rats, understood whether oxidative stress palyed an important roles in the development of the renal injury in hyperthyroidism; to investigate the expression of transforming growth factor -β₁ and Nestin in renal cortex of hyperthyroidism rats, researched the relationship between thyroid function and renal damnification ;the characters and pathogenesis of renal damnification in hyperthyroidism.Methods: The model of hyperthyroidism rat was made by giving them levothyroxine (L-T4) (50μg·100g^-1·d^-1).At the same time the rats lavaged by distilled water were named control group. The control groups(A) and hyperthyroidism groups(HT) were observed on 25d(A1 and HT1),45d(A2 and HT2) and 60d(A3 and HT3). Observed symptom and physical sign, thyroid function, renal function and pathological changes; renal tissue homogenate were collected for determination of renal cortex anti-oxidant enzyme activities and the level of MDA; used the immunohistochemistry to determine the expression of TGF-β₁ and Nestin in renal tissue; simultaneity tested Urine protein quantitation in 24 hours.Results: 1 Symptom and physical sign: The rats whose condition in drinking and eating, mental state, daily activities in control groups were normal, and the body weight of control groups were stably increased. Hyperthyroid rats showed drinking and eating more than control groups, the rat's dejecta was paste which contained undisjested; most hyperthyroid rats had trichomadesis and rarefaction; increased activity; irritated and with muscle microtremored; simultaneity the body weight were less than control groups (P<0.05),the ratio of kidney weight to body weight were more than control groups ( P<0.01).2 The thyroid function examinationThe level of FT3 and FT4 of hyperthyroidism groups were more significantly increased than control groups on 25d,45d,60d(P<0.01). The level of TSH were more obviously reduced than control groups. The thyroid function in HT1,HT2,HT3 also had remarkable difference. The observation of the increased level of FT3,FT4 and reduced level of TSH paralleled with the course of treatment with levothyroxine (L-T4) ( P<0.01).3 Serum creatinine,Urine protein quantitation in 24 hoursThe level of serum creatinine of hyperthyroidism groups were not more significantly increased than control groups on 25d,45d(P>0.05). The level of serum creatinine of 60d hypert- hyroidism group (HT3) was more significantly increased than control group (P<0.05), also higher than HT1 and HT2 groups.Urine protein quantitation in 24 hours of hyperthyroidism group was not more significantly increased than control group on 25d (P>0.05). Urine protein quantitation in 24 hours of hyperthyroidism groups were more significantly increased than control groups on 45d,60d (P<0.01). There were more significantly different between the three hyperthyroidism groups(P<0.01).4 Renal tissue homogenate variablesThe activity of CAT, GSH-Px, SOD of hyperthyroidism groups were more significantly decreased than control groups on 25d,45d,60d(P<0.01), which were aggravated progressively. The activity of CAT and SOD of HT3 were more obviously reduced than HT1 and HT2(P<0.01);the activity of GSH-Px of HT3 was lower than HT2(P<0.05) and more remarkably reduced than HT1(P<0.01). The activity of GSH-Px and SOD of HT2 were more significantly reduced than HT1(P<0.01) and the activity of CAT of HT2 was lower than HT1(P<0.05).The level of MDA of hyperthyroidism groups were more significantly increased than control groups(P<0.01), which were aggravated progressively.5 Pathological changesElectron microscope: In the control groups the structure of podocytes in glomcrulus was integrity, foot process lining up in order and clearly. In the hyperthyroidism groups glomerular basement membrane coiling irregularity; foot process of podocytes coalesce focally; the antilinear of capillary endothelium window increasing; crista mitochondriales of podocytes meromixis or to disappear; there is degranulation in rough endoplasmic reticulum; all of these aggravate following hyperthyroidism condition.6 The immunohistochemical stainingThe result of TGF-β₁: the expression of TGF-β₁ of control groups in renal cortex were not too much, the positive area was mainly located in endochylema; comparing to the control groups, the expression of TGF-β₁ of hyperthyroidism groups in glomerulus and renal tubule were enhanced along with the course of disease in the hyperthyroidism groups. Positive area ratio of TGF-β₁ of HT1 group was increased than control group on 25d (P<0.05). HT2 and HT3 groups were more significantly increased than control group on 45d and 60d(P<0.01).There were remarkable difference in HT1, HT2, HT3. Positive area ratio of TGF-β₁ of HT3 was more significantly increased than HT1 and HT2(P<0.01,P<0.05). Positive area ratio of TGF-β₁ of HT2 was also higher than HT1( P<0.05).The result of Nestin: Positive area ratio of Nestin of HT1 group was reduced than control group on 25d (P>0.05). HT2 and HT3 groups were more significantly reduced than control group on 45d and 60d(P<0.05,P<0.01). There were difference in HT1,HT2,HT3. Positive area ratio of Nestin of HT2 and HT3 were more significantly reduced than HT1(P<0.01). Positive area ratio of Nestin were not difference in HT2 and HT3.7 CorrelationThe activity of CAT,GSH-Px,SOD were significantly negative correlation with the level of FT₃, FT₄, and positive correlation with the level of TSH; the level of MDA significantly positive correlation with FT₃, FT₄, and negative correlation with TSH; the expression of TGF-β₁ were significantly positive correlation with FT₃, FT₄, and negative correlation with TSH; the expression of TGF-β₁ were significantly negative correlation with anti-oxidant enzyme activities, and positive correlation with the level of MDA. The expression of Nestin was significantly negative correlation with the level of FT₃, FT₄, and positive correlation with the level of TSH; the expression of Nestin was significantly positive correlation with anti-oxidant enzyme activities, and negative correlation with the level of MDA. Urine protein quantitation in 24 hours was significantly positive correlation with the level of FT₃,FT₄, and negative correlation with the level of TSH; positive correlation with TGF-β₁, and negative correlation with Nestin.(P<0.01)Conclusion: The model of hyperthyroidism rat was made by giving them levothyroxine (L-T4). Symptom, physical sign and thyroid function of hyperthyroid rats were accord with the characters of hyperthyroidism. Along with the course of hyperthyroidism, it were appeared with renal damnification, which displayed by kidney hypertrophy, increasing serum creatinine , albuminuria, reducing anti-oxidant enzyme activities, increasing the level of MDA. It was suggested that the effect of higher level of thyroid hormone could disturb normal renal physiologic function. It was also suggested that oxidative stress palyed an important roles in the development of the renal injury in hyperthyroidism. The expression of TGF-β₁ in renal cortex were associated with the process of hyperthyroidism, and were significantly correlation with oxidative stress. It was showed that TGF-β₁ may be also related to ROS in kidney injury, accordingly producing albuminuria and finally glomerular sclerosis. The observation of the reduced expression of Nestin demonstrated that the pathological changes of renal were related with process of hyperthyroidism, which paralleled with thyroid function. It was showed that podocyte injury may played an important roles in hyperthyroidism renal damnification.