ABSTRACT
ObjectiveTo observe the expression of syntaxin-1 in hippocampus of adult rats with hypothyroidism and the role of different doses of thyroid hormone replacement therapy,further to explore the molecular mechanism of brain damage.MethodsAll 44 male adult SD rats were randomly divided into 4 groups according to their body mass(250 - 300 g):hypothyroidism group,routine dosage thyroxine treatment group,high dosage thyroxine treatment group and control group (11 in each group).Hypothyroidism group,routine dosage thyroxine treatment group and high dosage thyroxine treatment group received daily intraperitoneal injection of propylthiouracil (PTU) 10 mg/kg.Hypothyroidism group was given PTU by intraperitoneal injection for two weeks after the previous four week treatment,the routine dosage thyroxine treatment group and the high dosage thyroxine treatment group were given 50,200 μg/kg L-thyroxine daily intraperitoneally for two weeks; the control group received daily intraperitoneal injection of saline.The levels of serum T3,T4 were assayed by radioimmunoassay method,and the level of syntaxin-1 in hippocampus was analyzed by immunohistochemistry.ResultsIn the hypothyroidism group,the levels of serum T3,T4[(0.34 ± 0.04),(43.01 ± 2.95)nmol/L] were significantly lower than those in the control group[(0.65 ± 0.05),(55.20 ± 3.56)nmol/L,all P ＜ 0.05].In the routine dosage of thyroxine treatment group,the levels of serum T3,T4[(0.63 ± 0.05),(55.04 ± 3.77)nmol/L] were not significantly different compared to the control group (all P ＞ 0.05 ).In the high dosage thyroxine thyroid hormone treatment group,the levels of serum T3,T4[(1.11 ± 0.10),(96.68 ± 6.42)nmol/L] were significantly higher than those in the control group(all P ＜ 0.05).The levels of syntaxin-1 protein in the CA1,CA3 and dentate gyrus(DG) of all layer regions of hippocampus (0.059 ± 0.016,0.064 ± 0.014,0.068 ± 0.016,0.069 ± 0.017,0.072 ± 0.016,0.070 ± 0.011,0.051 ± 0.012,0.072 ± 0.017) were significantly higher compared to the control group(0.037 ± 0.008,0.045 ± 0.010,0.042 ±0.009,0.040 ± 0.010,0.053 ± 0.009,0.042 ± 0.009,0.032 ± 0.007,0.047 ± 0.010,all P ＜ 0.05).In the routine dosage and the high dosage thyroxine thyroid hormone treatment group,the level of syntaxin-1 in CA1,CA3and DG regions(0.041 ± 0.011,0.046 ± 0.017,0.044 ± 0.014,0.037 ± 0.008,0.051 ± 0.010,0.043 ± 0.010,0.033 ± 0.011,0.045 ± 0.014 and 0.040 ± 0.010,0.045 ± 0.011,0.043 ± 0.010,0.033 ± 0.009,0.050 ± 0.010,0.041 ± 0.009,0.032 ± 0.009,0.046 ± 0.009)were not significantly different compare to the control group(all P＞0.05).ConclusionThe expression of syntaxin-1 in hippocampus of adult-onset hypothyroidism is increased,which can be reversed by routine dosage treatment of thyroxine.
ABSTRACT
Objective To observe the expression of synaptotagmin I(syt I)protein in the prefrontal cortex of adult-onset hypothyroidism rats and the effects of replicated therapy in different doses of thyroid hormone on the syt I protein.Methods All 44 aduh male Sprague-Dawley rats were divided into 4 groups randomly according to their body mass:hypothyroidism group,routine dosage thyroxine treatment group,high dosage thyroxine treatment group and control group.The adult male Sprague-Dawley rats were replicated to the adult-onset hypothyroidism and treatment models with propyhhiouracil(PTU).The levels of serum T3,T4 were assayed by the radioimmunoassay method and the level of the syt I protein in the molecular layer,external granular layer,external pyramidal layer,internal granular layer and internal pyramidal layer in prefrontal cortex was analyzed by immunohistochemistry.Results In the hypothyroidism group,the levels of serum T3 and T4[(0.34±0.04),(43.01±2.95)nmol/L]were significantly lower than those in the control group[(0.65±0.15), (55.20±3.56)nmol/L, F value: 6.026,5.940,4.503,P<0.05 or <0.01 ], the levels of the syt I protein in the molecular layer(0.018±0.010), external granular layer (0.020±0.007), external pyramidal layer(0.013±0.008), internal granular layer(0.011±0.005), internal pyramidal layer(0.024±0.013) of prefrontal lobe were significantly lower compared to the control group[(0.028±0.010,0.031 ± 0.010,0.028 ± 0.010,0.022 ± 0.008,0.038 ± 0.013), F value: 5.697,8.965,14.668,13.597,6.807,P<0.05 or <0.01 ]. In the routine dosage of the thyroxine treatment group, the levels of serum T3,T4 [(0.63 ±0.05), (55.04 ± 3.77)nmol/L] were not significantly different compared to the control group(F value: 3.162,0.367,all P>0.05), and the level of the syt I protein in the molecular layer, external granular layer, external pyramidal layer, internal granular layer and internal pyramidal layer in prefrontal cortex showed a significant improvement of the syt I protein(0.027 ± 0.013,0.025 ± 0.009,0.022 ± 0.008,0.020 ± 0.010,0.033 ± 0.010), which were similar to that of the control group(F value: 0.094,2.208,2.467,0.350,0.693, all P>0.05). In the high dosage thyroxine thyroid hormone treatment group, the levels of serum T3 and T4[ (1.11 ± 0.10), (96.68 ± 6.42)nmoL/L] were higher than the control group(F value: 6.291,12.031, all P<0.01), the expression of the syt I protein(0.028 ± 0.008,0.031 ±0.011,0.026 ± 0.012,0.023 ± 0.011,0.038 ± 0.010) were not significantly different compare to the control group (F value: 0.001,0.019,0.111,0.061,0.001, all P>0.05). Conclusions The expression of the syt I protein in the prefrontal cortex of adult-onset hypothyroidism can be decreased, which can be reversed by routine dosage of thyroxine treatment.
ABSTRACT
Objective To observe the effect of different thyroid hormone level on the expression of synaptotagmin Ⅰ(Syt Ⅰ) in adult rat hippocampus. Methods All 28 adult male SD rats were assigned randomly into hypothyroid, hyperthyroid and control group, hypothyroid group was established by daily intraperitoneal injections with propylthiou raci(PTU, 10.0 mg/kg body weight) for 6 weeks and hyperthyroid group with L-Thyroxine (L-T4, 0.5 mg/kg body weight) for 3 weeks. Radioimmunity method was used to assay the levels of serum T3 and T4, immunohistochemical S-P technology to assay the levels of Syt Ⅰ protein in hippoeampus CA1, CA3 and dentate gyrus (DG). The layers analyzed in the different subfields include the polymorphic cell layer(the stratum oriens, SO), pyramidal cell layer(PCL), stratum radiatum (SR), lacunosum-molecular layer (SLM) in CA1 and CA3, granular cell layer(GL) and molecular layer(ML) in DG. Results The levels of serum T3 and T4[(0.34±0.12), (41.03± 11.37)nmol/L]in the hypothyroid rats were significantly lower than those in the control group[(0.65±0.15), (55.20±10.68)nmol/L, P < 0.01 or < 0.05], and the positive granule of Syt Ⅰ was significantly lower in PCL and SR of CA1 and CA3, GL of DG. The average optical value responsible for Syt Ⅰ immunoreactivity was obviously reduced in SO(0.048±0.007), PCL(0.299±0.035), SR(0.042±0.007), SLM(0.038±0.006) of CA1, PCL(0.085± 0.019), SR(0.040±0.011), SLM (0.038±0.006) of CA3, GL (0.076±0.019) of DG than normal controls (0.068± 0.014, 0.376±0.053, 0.053±0.008,0.056±0.009,0.118±0.026,0.052±0.010,0.053±0.009,0.099±0.015; P< 0.01 or < 0.05). Serum T3 and T4 levels [(1.43±0.30), (157.18±19.95)nmol/L]of hyperthyroid rats were significantly higher than those of control group(P < 0.01). The value was reduced in PCL(0.322±0.050), SR(0.039±0.006), SLM (0.042±0.006) of CA1, PCL(0.098±0.034), SR(0.046±0.013), SLM(0.046±0.010) of CA3 and GL(0.085± 0.024), ML (0.042±0.009) of DG (P < 0.05 or < 0.01). Conclusion Adult-onset of hypothyroidism and hyperthyroidism can reversibly decrease the expression of Syt Ⅰ in CA1, CA3 and DG regions of hippocampus.
ABSTRACT
Adult male Kunming mice were divided into normal control group,propylthiouracil(PTU) treated group and PTU+T_4 treated group.Neurogranin(Ng)protein expression in the hippocampus after 8 weeks was assayed by Western blotting and immunohistochemical method.Results showed that Ng protein was decreased in the hippocampus of male mice with adult-onset hypothyroidism,suggesting that decreased Ng,which is correctable by T_4,is involved in cognitive dysfunction in adult-onset hypothyroid male mice.