| Background: Although many observational investigations have showed that male is the independent one of risk factors of coronary heart disease, up to date, we did not have enough evidences to support the conception that androgen will increase the incidence of coronary heart disease. Oppositely, it has been showed that the plasma concentration of male sex hormone will decrease with aging, and that the population who had higher coronary heart disease incidence would have lower testosterone concentration. Recently, some researches have reported that testosterone treatment will improve the prognosis of heart failure. In the present study, high and low doses testosterone will be used in castrated male SD rats 6 hours after acute myocardial infarction. The influence on AMI left ventricular remodeling, nerve remodeling, cardiac function and RYR2, RYR2 phosphorylated protein and FKBP12.6 protein level which are the key components of excitation-contraction coupling will be evaluated on the basis of systematically scanning its effect on liver, renal function and lip profile.Methods: Two weeks after male SD rats castrated, left anterior descending artery was ligated to prepare AMI model. 6 hours after AMI, high and low doses testosterone and placebo were randomly given intramuscularly to 5 groups: S-Cas+MI+P (n=6), Cas+ S-MI+P (n=6), Cas+MI+P (n=ll), Cas+MI+T (n=13), Cas+MI+t (n=12), and the death was recorded. After 6 weeks treatment, the hemodynamic indexes which including BP, LVEDP, LV±dp/dtmax were determine. Then, the rats were killed and the hearts and serum samples were harvested, and the left atrium thrombus incidence were recorded. The serum was used to determine the serous TG, TC, HDL, LDL, GPT, Cr, NE, ANP and testosterone. HE staining, picrosirius red staining and anti-TH immunochemical staining were donein the paraffin imbedding upper part of every heart. The lower part of every heart was homogenized and the protein level of RYR2, phosphorylated RYR2 and FKBP12.6 were semi-quantified with Western-blot method.Results: model reliability: Infarction size in Cas+MI+P, Cas+MI+T, Cas+ Ml+t and S-Cas + MI +P were 47.6 + 5.0%, 49.7±3.3%, 46.2+3.3% and 48.2 +2.8%, respectively, and there was no significant difference among the four groups, P>0.05. serous testosterone concentration in Cas+MI+T, Cas+MI+t, S-Cas + MI +P were 138.15 +13.62ng/ml, 40.45 ± 11.13ng/ml and 1.78 + 0.09ng/ml, respectively. Cas + MI+P and Cas+S-MI+P serous testosterone concentration were nearly lowered to zero.Myocardial tissue collagen volume fraction(CVF): The CVF in the non-infarction area of Cas + MI+P was significantly lower than that of Cas+S-MI+P (8.0±2.1% vs 17.2+4.9%, PO.01). The area of Type I and type III and the ratio of type I to type III collagen in the infarction area were nearly the same in Cas+MI+P and S-Cas + MI +P, but CVF of non-infarction area in Cas+MI+P was significantly lower than that of S-Cas + MI +P (8.0 + 2.1% vs 13.4 + 5.7%, P<0.01). Cas + MI+T type III collagen volume in infarction area was significantly higher than that of Cas+MI+P (104044.2 + 55743.8, 49576.0 ±28226.2, PO.01), while, type I collagen volume in the same area was significantly lower in Cas + MI+T than that of Cas + MI+P (273850.6 ±67188.1, 393278.8 ±74650.1, P<0.01). The ratio of type I to type III collagen was significantly inversed in the Cas+MI+T than that of Cas+MI+P. The CVF in non-infarction area of Cas+MI+T and Cas+MI+P didn't differ significantly. Compared with that of Cas+MI+P, type III collagen volume in infarction area of Cas+MI+t was significantly lower (23491.6± 12439.1 vs 49576.0 + 28226.2, PO.01), while, type I collagen volume was not differ significantly. The ratio of type I to type III collagen was higher in Cas+MI+t than that of Cas+MI+P (8.3 + 8.5 vs 12.3 + 10.7, P=0.25), but did not differ significantly. CVF in the non-infarction area of Cas+MI+t was significantly higher than that of Cas + MI+P. Cas + Ml+t type III collagen volume in infarction area was significantly lower than that of Cas+MI+T, while type I collagen volume was significantly increased. The ratio of type I to type III collagen in infarction area was significantly higher in Cas+MI+t than that of Cas +MI+T(P<0.01).Either castration or T treatment did not cause any significant difference of infarction area wall thickness among the above all groups. Compared with that of Cas+S-MI+P, MCSA of Cas+MI+P was significantly higher (275.09+15.10 urn2 vs 200.50±14.42 urn2, P<0.01), and lower dose T administration also caused MCSA increased significantly than that of Cas+MI+P (319.78 ±52.42 urn2 vs 275.09± 15.10 urn2).Body weight(BW) and ventricular weight: There is no significant difference of body weight before the treatment among Cas+MI+P, Cas+MI+T, Cas+MI+ t. 6 weeks after T treatment, BW of Cas+MI+T was significantly lower than that of Cas+MI+P (P<0.01), while BW of Cas+MI+P and Cas+MI+t did not differ significantly. BW increments of Cas+MI+P, Cas+MI+T and Cas+MI+t were 74.00±18.97g, 34.70±25.40g and 69.82±15.38g, respectively. BW increment of Cas+MI+T was significantly lower than those of Cas+MI+P and Cas+MI+t, while BW increment did not differ significantly between Cas+MI+P and Cas+ Ml + t. Relative ventricular weight (RVW), relative left ventricular weight (RLVW), relative right ventricular weight (RRVW) and the ratio of right to left ventricular weight (RRLVW) did not differ significantly between Cas+MI+P and S-Cas + MI +P. RVW, RRVW and RRLVW of Cas+MI+P were significantly higher than those of Cas+S-MI+P (PO.01), while RLVW did not differ significantly between these two groups. RVW, RRVW, RRLVW did not differsignificantly among Cas+MI+P, Cas+MI+T and Cas+MI+t, while RLVW of Cas+MI+t was significantly higher than that of Cas+MI+P (2.42+0.23 vs 2.15 +0.18, PO.01), and RLVW did not differ significantly between Cas+MI+P and Cas+MI+T.Hemodynamic results: Compared with those of Cas+S-MI+P, SBP, DBP, LV+dp/dtmax and LV-dp/dtmax of Cas+MI+P were significantly decreased, while LVEDP was significantly increased. LVEDP, LV+dp/dtmax, LV-dp/dtmax did not differ significantly between Cas+MI+P and S-Cas+MI+P. Compared with those of Cas+MI+P, LVEDP of Cas + MI+T and Cas + MI+t decreased significantly (PO.01), while LV-dp/dtmax slightly, but not significantly increased in Cas+ MI+T and Cas+MI+t (5765.6± 1342.9 mmHg/s vs 4696.7+1538.4 mmHg/s, 5678.0 + 1078.5 mmHg/s vs 4696.7 + 1538.4 mmHg/s), and LV+dp/dtmax significantly increased in Cas+MI+t. Cas+MI+T and Cas+MI+t did not differ significantly in above indexes.Serous indexes: Although all groups were administrated with different interferences, serous GPT and Cr concentration were still in normal range. Compared with those of Cas+S-MI+P, serous ANP and NE concentration was significantly increased in Cas+MI+P (PO.01), while ANP did not differ significantly between Cas+MI+P and S-Cas+MI+P. Compared with those of Cas+MI+P, PT administration decreased serous ANP and NE significantly(ANP: 0.93+0.14 pg/mLvs 1.31 ±0.42 pg/mL, 0.81+ 0.14 pg/mLvs 1.31+0.42 pg/mL, PO.05;NE: 2.02±0.49 ng/mL vs 7.21 +0.63 ng/mL, 3.37+0.56 ng/mL vs 7.21 + 0.63 ng/mL, P<0.01), while ANP and NE did not differ significantly between Cas+MI+T and Cas+MI+t.Sympathetic nerve density and distribution: Compared with that of Cas+S-MI+P, sympathetic nerve density (SND) in non-infarction area of Cas+MI+P decreased significantly, (1571.3+395.1 umW vs 2964.0±1141.2um2/mm2, PO.01). SND and regional heterogeneity did not differ between Cas+MI+P and S-Cas+MI+P. Compared with those of Cas+MI+P, PT administration increased infarction area SND and regional heterogeneity significantly (SND: 7302.0 + 4962.6 umW vs 2647.8 ± 1286.5 umW, 9701.2 + 5859.7 um2/mm2 vs 2647.8 ± 1286.5 umW, P<0.05;regional heterogeneity: 6014.0+4385.1 um2/mm2 vs 712.5±370.9 um2/mm2, 6663.6+ 1094.9 umW vs 712.5+370.9 um2/mm2, PO.05), while SND and regional heterogeneity in the non-infarction area did not differ significantly. SND and regional heterogeneity did not differ significantly between Cas+MI+T and Cas-f Ml+t.Western-blot results: Compared with those of Cas+S-MI+P, the protein level of FKBP12.6 and RYR2 decreased significantly, while protein level of phosphorylated RYR2 and relative RYR2 phosphorylation ratio increased significantly (PO.01). Protein level of phosphorylated RYR2 and relative RYR2 phosphorylation ratio was significantly higher in Cas+MI+P than that in S-Cas+MI+P (PO.01), while Protein level of FKBP12.6 did not differ between these two groups. Compared with those of Cas+MI+P, PT administration increased protein level of RYR2 significantly, and decrease Protein level of phosphorylated RYR2 and relative RYR2 phosphorylation ratio significantly. Additionally, high dose T increased protein level of FKBP12.6 significantly than that of Cas+MI+P, while low dose T did not show this kind of effect. Protein level of RYR2 and FKBP12.6 were high in Cas+MI+T than those in Cas+MI+t.Conclusion: According to our experiment results we obtain the following conclusion: PT administration will decrease mortality of MI. Low dose T had potential to accelerate the healing process of infarction area, oppositely, high dose T had delayed this process. This result suggested that T efficacy on ventricular remodeling had significant dose dependent. T administration decreased LVEDPand ANP, and increased LV+dp/dtmax significantly. So it had potential to improve left ventricular function. T administration caused peri-infarction area sympathetic nerve density and regional heterogeneity increased, while plasma NE decreased. MI caused protein level of FKBP12.6 and RYR2 decreased, and protein level of phosphorylated RYR2 and relative RYR2 phosphorylation ratio increased. T administration inverted this kind of alterations. This result suggested that T administration could improve RYR2 function, which is the key component of excitation-contraction coupling.
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