Antihypertension and anti-cardiovascular remodeling by phenylalanine in spontaneously hypertensive rats: effectiveness and mechanisms

苯丙氨酸对自发性高血压大鼠的抗高血压和抗心血管重塑的效果和机制

odeling · mechanismObjective To investigate mechanisms of anti hypertension and anti cardiovascular remodeling by phenylalanine (phe) in spontaneously hypertensive rats (SHRs) Methods The comparison of blood pressure (BP) increment with the ages and cardiovascular changes of SHRs was made between the 3% phe intervented group (SHR phe) and the control SHRs group Detection of the structural changes with the VIDAS digital vedio frequency processing technique and light and electron microscopy were made The cell growth and proliferation of cultured smooth muscle cells (CSMCs) of the thoracic aortas or myocardial fibroblasts were evaluated by measuring the 3 H thymidine counts per minute (cpm) incorporated into the new synthesized desoxyribonucleic acid (DNA) and determining the cell number with the crystal violet stain technique The Ca 2+ influx was measured in counts/min of 45 CaCl 2 after incubating it with 5 different concentrations of phenylalanine and the intracellular [Ca 2+ ] i by Fura Ⅱ/Am indicator The total messenger ribonucleic acid (mRNA) of the myocardium was extracted and Northern blot analysis was performed with the probe collagen α 2(Ⅰ)cDNA The tyrosine hydroxylase (TH) activity was measured by high performance liquid chromatography (HPLC) with electrochemical detector after having reacted with its substrate tyrosine and other reagents The catecholamine contents in brain homogenat were detected by HPLC method The comparison of pharmacokinetics of phenylalanine among SHR phe, SHRs and control Wistar Kyoto (WKY) rats was made after intravenous injection of 3 H L phe (1?ml/kg) by PK GRAPH Program for kinetic calculation The 3H L phe uptake by CSMCs after incubating for difinite intervals was also detected and compared Results Phenylalanine could prevent the increase of BP with ages and the heart weight (heart/body weight index) The aortic media thickness and the collagen content in the myocardium were decreased significantly in SHR phe Whereas the dearranged cardiovascular structure was much improved The mechanisms might be direct and specific inhibition of the DNA synthesis and proliferation of cardiovascular cells which may be related to the inhibition of collagen α 2(Ⅰ)cDNA, c fos and c myc expression Other mechanisms may include decrease of intracellular [Ca 2+ ] i and an inhibition of central sympathetic activity due to the results of higher TH activity in the caudate nucleus and higher adrenaline content in the posterior hypothalamus Besides, partial recovery of phenylalanine metabolic aberrants existed in SHRs seems to be another possibility for its effectiveness Conclusions Phenylalanine intervention could exert a definite anti hypertension and anti cardiovascular remodeling effects on SHRs like seen in human essential hypertension Its mechanisms might be related to direct inhibition of growth in the cardiovascular cells, decrease of central sympathetic activity, the reverse of the exhibited phenylalanine metabolic aberrants in SHRs, and a decrement of intracellular [Ca 2+ ] i

目的 阐明苯丙氨酸 (phe)在自发性高血压大鼠 (SHR)中的抗高血压和抗心血管重塑的效果和机制。方法 4 - 6周龄SHRs鼠用或不用 3%phe的饲料进行干预 ,比较两组间血压及心血管变化。用VIDAS数字式视频处理技术、光学显微镜及透射电镜检测心血管结构变化。测量胸主动脉平滑肌细胞 (CASMCs)的 [3H]胸腺嘧啶放射性计数 (cpm)和用结晶紫染色法测量细胞数目。Smith法测定Ca2 +内流 ,Grynkic法测量 [Ca2 +]i。心肌总mRNA进行Northernblot分析。HPLC法测定酪氨酸羟化酶 (TH)活性。用HPLC测定脑组织儿茶酚胺含量。静脉注射3H L phe(1ml/kg)后进行动力学计算。测定和比较CASMCs对3H L phe的摄取。结果 Phe能 (1)阻止血压和心重 /体重比值随年龄的增加。减少SHR phe组大鼠主动脉中层厚度和胶原含量 ;(2 )抑制胶原α2 (I)mRNA、c fos和c myc表达 ;降低细胞内 [Ca2 +]i;增高尾核TH活性和下丘脑肾上腺素含量 ;(3)部分逆转phe动力学异常。结论 幼龄SHR鼠用Phe干预具有抗高血压和抗心血管重塑作用。机制可能是 :直接抑制心血管细胞生长 ;降低中枢交感神经活性 ;逆转phe的代谢异常和降低细胞内 [Ca2