Effects Of Ractopamine On The Expression Of Vimentin Of Testis In Male Adult Rats

ObjectiveThis study was carried out to investigate the effects of ractopamine on the expression of vimentin of testis in male adult rats after administration for Id and 14d with different dosages and withdrawal periods. After that, it would explore the effects of ractopamine on testis and the possible mechanisms which would provide experimental data for further studies about effects ofβ2-androgen agonists on male reproductive system and food safety.Materials and Methods1. Animals and ChemicalsAll adult male Sprague-Dawley (SD) rats (9-10 weeks, weighing 200-220 g, specific pathogen-free grade) were housed under conventional laboratory conditions. Animals were allowed access to commercial pellet food and tap water ad libitum and allowed one week's acclimatization before the experiments. All rats were maintained on a 12-h light/dark cycle throughout the experiment. RAC was dissolved in 0.9% NaCl solution up to 1 ml and was given to the animals by gavage on a specific time. The control groups were given the 0.9% NaCl solution instead.2. Groups and the administration2.1 Experiments of 1-d treatmentThirty-five rats were randomly divided into seven groups and allowed one week's acclimatization before the experiments. RAC was dissolved in 0.9% NaCl solution up to 1 ml and was given to the animals by gavage for 1 day. The dosages were group A (200 mg kg-1 bw day-1), group B (20 mg kg-1 bw day-1), group C (2 mg kg-1 bw day-1), group A (200 mg kg-1 bw day-1), group B'(20 mg kg-1 bw day-1), group C (2 mg kg-1 bw day-1) and group K (0 mg kg-1 bw day-1). Groups A, B and C received a 1-d withdrawal period and groups A', B'and C received a 7-d withdrawal period before death. Group K was the control and was given the 0.9% NaCl solution instead.2.2 Experiments of 14-d treatmentSixty-five rats were randomly divided into thirteen groups and allowed one week's acclimatization before the experiments. RAC was dissolved in 0.9% NaCl solution up to 1 ml and was given to the animals by gavage for 14 days. The dosages were group D (200 mg kg" bw day-1), group E (20 mg kg-1 bw day-1), group F (2 mg kg-1 bw day-1), group D'(200 mg kg-1 bw day-1), group E'(20 mg kg-1 bw day-1), group F'(2 mg kg-1 bw day-1), group H (2 mg kg-1 bw day-1), group I (0.2 mg kg-1 bw day-1), group J (0.02 mg kg-1 bw day-1), group H'(2 mg kg-1 bw day-1), group I'(0.2 mg kg-1 bw day-1), group J'(0.02 mg kg-1 bw day-1) and group K'(0 mg kg-1 bw day-1). Groups D-F and groups H'-J'received a 7-d withdrawal period, groups D'-F'received a 21-d withdrawal period, groups H-J received a 7-d withdrawal period before death. Group K' was the control and was given the 0.9% NaCl solution instead.3. MethodsThe body weights and testis wet weights of all rats were recorded. The vimentin mRNA expression in testis was determined by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The vimentin and StAR protein expression in testis were determined by western blotting. All data were expressed as mean±SD (x±s). Statistical analysis was performed using SPSS 13.0 on computer. Statistical significance was accepted at the P<0.05 level.Results1. Body weights and testis wet weightsTestis wet weights, body weights and their ratios in 1-d experiments had no significant difference compared with the control except group A' (P>0.05); The body weights in groups D-F, D'-F'and H'all increased significantly compared with the control (P<0.05). Testis wet weights and the ratios of testis wet weight to body weight in 14-d experiments had no significant difference compared with the control (P>0.05).2. The vimentin mRNA expression in testisThe RT-PCR results showed that the vimentin mRNA expression in testis in 1-d experiments had no significant difference compared with the control group (P>0.05). But the vimentin mRNA expression increased significantly compared with the control in groups D, E, D' and E'in testis in 14-d experiments (P<0.05).3. The vimentin and StAR protein expression in testis The western blotting results showed that the vimentin and StAR protein expression in 1-d experiments all had no significant difference compared with the control (P>0.05). The vimentin protein expression in groups D, E, D', E'and H all increased significantly in 14-d experiments (P<0.05). However, the StAR protein expression in groups D-F'and H decreased significantly compared with the control (P<0.05).Conclusions1. RAC could increase the body weight of rats, but had little effect on testis wet weights. The statistical results showed that RAC could increase the body weight by promoting the synthesis and decreasing the decomposition of proteins.2. RAC could increase the vimentin mRNA expression. The RT-PCR results showed that RAC could affect the vimentin mRNA expression in the transcription level and the effects had a dose-time related.3. RAC could increase the vimentin protein expression and had an increasing trend with the dosage increasing. The western blotting results showed that RAC could affect and cause an up-regulation of the vimentin protein expression in the translation level. Whether the up-regulation of vimentin cause damage to the testis needs further studies.4. RAC could decrease the StAR protein expression and had a dose-time related. Results showed that RAC could affect and cause a down-regulation of the StAR protein expression in the translation level. The down-regulation of StAR can decrease the synthesis of androgen and affect the function of normal cells in testis.