Research Of Preventive Effect And Mechanism Of Taurine On Hypertension In Rats

Taurine was found to be one of the most abundant free amino acids in cardiovascular tissues of animals,but its preventive effects on hypertension is still obscure.In the present study,the effects of taurine on hypertension was investigated.In experiment 1,male rats were given tap water containing taurine and L-NAME(inhibitor of NOS),then the preventive effect and mechanism of taurine on hypertensive induced by L-NAME were investigated.100 male wistar rats were randomly divided into five groups. The rats in the control group were given normal diet and tap water.The rats in the model groupâ… were given normal diet and tap water containing 75mg/100ml of L-NAME,model groupâ…¡were given normal diet and tap water containing 75mg/100ml of L-NAME and 1%β-Ala.Prevention groupâ… were given normal diet and tap water containing 75mg/100ml of L-NAME and 1%taurine.Prevention groupâ…¡were given normal diet and tap water containing 75mg/100ml of L-NAME and 2%taurine.Blood pressure was detected using tail-cuff method every two days.The results showed that 1 week later,blood pressure in the model group increased and the increase lasted in the following three weeks.There is no significant difference between the modelâ… andâ…¡groups,and the blood pressure of model groupâ…¡is a little higher than that of the model groupâ… .Blood pressure in prevention groupâ… was lower compared with the model groups and there is no significant difference between prevention groupâ…¡and the control group.The results indicated that the model of hypertensive rats was established by L-NAME which could induce hypertension.Taurine could inhibit the elevation of blood pressure.In experiment 2,experimental animals were selected from experimentâ… .The rats were killed respectively at the end of the third and the fourth weeks.The contents of serum calciumion,sodiumion,TNF-α,IGF-â… ,plasma PRA,ADM,CGRP,ALD and the contents of cAMP,cGMP in cardiac muscle were detected.The results showed that the contents of TNF-α, ALD and PRA increased significantly compared with the control group(p＜0.05),the prevention groups significantly decreased in model groups(p＜0.05),the effect of prevention groupâ…¡is better than that of the prevention groupâ… ,the contents of CGRP and cGMP significantly decreased compared with the control group(p＜0.05),the prevention groups significantly increased the in model groups(p＜0.05),the effect of prevention groupâ…¡is better than that of prevention groupâ… ,but there was significant differences in the level of ADM, IGF-â… ,Ca²⁺,Na⁺ ana cAMP(p＞0.05).Conclusion:the preventive mechanisms of taurine on hypertension may due to the following reasons:it could restrain RAAS activity,inhibit the secretion of cell factor PRA,TNF-αand ALD secretion,increase the plasma level of CGRP and the level of cGMP in ardiac muscle.In experiment 3,abodominal aortas selected from experimentâ… were fixed in phosphate buffered formalin solutions and were embeded in paraffin wax.Sections were cut and stained with haematoxylin and eosin(HE).Proliferations of vascular smooth muscle cells(VSMC) were observed under optical microscope.The results showed:VSMC in the model groups significantly proliferated,the vessel wall thickened significantly.The number of VSMC in prevention groupâ… was less than that of the model groups.The VSMC in prevention groupâ…¡proliferated a little.The results indicated that taurine could inhibit the proliferation of VSMC obviously and the effect of 2%taurine is better than that of 1%tauine,which can be regarded as another preventive mechanisms of taurine on hypertension.In experiment 4,MTT method was used to study the effects of taurine on the proliferation of VSMC.In this experiment,taurine(0.1μg/mL,1μg/mL,10μg/mL,100μg/mL,500μg/mL,1 000μg/mL) and Angâ…¡(1×10^-7 moL/L) were addes in the culture fluid of VSMC in arteria femoralis.The results showed that taurine could significantly inhibit the proliferation of VSMC,which indicated that taurine could inhibite the proliferation of VSMC induced by Angâ…¡.In experiment 5,rats selected from experimentâ… were killed at the end of the fourth week. At the same time,cardiac muscle,lung and adrenal gland were taken out promptly,then total RNA were extracted.The influence of taurine on the expression of receptors ofβ2-AR mRNA, AC5 mRNA,cAMP mRNA in cardiac muscle,ACE mRNA in cardiac muscle and lung,AGT mRNA,ATR1a mRNA and ATR2 mRNA in adrenal gland were detected by real time PCR. The results showed that taurine could decrease the expression level of ACE mRNA in cardiac muscle and lung,AGT mRNA,ATR1a mRNA,and increase the expression level of ATR2 mRNA.There were no significant differences between the control group and the taurine groups.The effects of taurine on the expression level ofβ2-receptor mRNA and AC5 mRNA were not significant.So it could be concluded that taurine may prevent hypertension by way of decreasing the expression level of ACE mRNA in cardiac muscle and lung,AGT mRNA and ATR1a mRNA in adrenal gland,increasing the expression level of ATR2 mRNA in adrenal gland,thus it could inhibit the production of Angâ…¡directly or indirectly,and inhibit the production of ATR1a,promote the production of ATR2.