小牛血清去蛋白注射液对大鼠局灶性脑缺血再灌注后Caspase-12表达的影响

目的 探讨小牛血清去蛋白注射液(DCSI)对脑缺血再灌注后大鼠海马Caspase-12表达的影响.方法 健康SD大鼠随机分为假手术组、模型组和DCSI组.DCSI组于术前1 w开始给药,每日大鼠尾静脉注射DCSI 80 mg/kg,末次给药5 h后建立脑缺血再灌注模型.分别在脑缺血再灌注后的5个时间点进行神经行为学观察,海马病理学、细胞凋亡、Caspase-12蛋白及mRNA表达指标的检测.结果 与假手术组相比,模型组大鼠脑缺血再灌注后的神经功能缺损明显,海马细胞呈明显凋亡表现,Caspase-12蛋白及mRNA表达上调,尤以24h时明显(P＜0.01);DCSI组与模型组相比,功能缺损评分和细胞凋亡相对较轻,Caspase-12蛋白及mRNA表达也相对下凋(P＜0.01,P＜0.05).结论 DCSI对缺血再灌注损伤大鼠大脑具有保护作用,其机制可能与其有效抑制脑组织Caspase-12 mRNA转录水平及蛋白表达、阻断内质网应激启动的凋亡通路有关.     

大鼠心肌缺血/再灌注损伤心肌细胞凋亡与Fas、FasL基因表达的变化

目的：探讨大鼠实验性心肌缺血再灌注时心肌细胞凋亡与Fas及Fas蛋白配体（Fas Ligand,FasL）基因表达的变化及与心肌组织损伤的关系。方法：以穿线结扎或松扎左冠状动脉制备大鼠心肌缺血再灌注模型。64只大鼠随机分成假手术组（假手术24h）、缺血再灌注I组（缺血30min、再灌注24h）、缺血再灌注Ⅱ组（缺备30min、再灌注72h）及缺血再灌注Ⅲ组（缺血3h、再灌注24h）。以缺口末端标记法检测心肌细胞凋亡的变化,S－P免疫组化法分别检测Fas与FasL蛋白水平变化,采用逆转录聚合酶链反应法检测Fas基因mRNA的表达改变,并分析心肌组织病理学损伤程度。结果：心肌缺血再灌注后心肌细胞凋亡指数Fas蛋白阳性染色指数与炎性细胞FasL蛋白阳性染色指数均增加,且均随缺血或再灌注时间延长而进一步增高; Fas基因的mRNA表达也上调,但以再灌注24h时达高峰;心肌缺血再灌注后心肌组织呈大小不一的灶性坏死,坏死周围有爆炸性一细胞浸润。结论：心肌缺血再灌注时心肌细胞凋亡、Fas基因的蛋白与mRNA表达水平及炎性细胞的FasL蛋白表达量均增加,心肌细胞凋亡与Fas/FasL系统参与了心肌缺血再灌注损伤过程。     

黄体酮对大鼠局灶性脑缺血再灌注损伤后脑组织神经生长因子表达的影响

目的 观察黄体酮对大鼠局灶性脑缺血-再灌注损伤后缺血区皮层神经生长因子(NGF)和脑源性神经营养因子(BDNF)在mRNA与蛋白质水平表达的影响,探讨黄体酮在脑缺血-再灌注损伤中的脑保护作用机制. 方法 采用SD雄性大鼠局灶性脑缺血-再灌注损伤模型.将96只大鼠随机分为4组:假手术组、缺血再灌注组、溶剂组和黄体酮组各24只.应用Real time-PCR和Western blot技术分别对缺血区皮层NGF和BDNF mRNA与蛋白表达情况进行测定. 结果 在缺血区皮层,缺血2h再灌注6h后,缺血再灌注组NGF和BDNF的mRNA及蛋白质表达达高峰,再灌注24 h后,回复到假手术组水平;缺血2h再灌注12 h后,黄体酮组NGF和BDNF mRNA及蛋白表达达高峰,再灌注24 h后,表达仍高(P＜0.05). 结论 黄体酮可以使脑缺血-再灌注损伤后NGF和BDNF的mRNA表达上调,促进脑内NGF和BDNF蛋白的合成,从而发挥脑保护作用.     

Toll样受体4在大鼠心肌缺血再灌注损伤中表达的实验研究

目的 观察心肌缺血再灌注早期Toll样受体4 mRNA(TLR4 mRNA)及蛋白表达,探讨TLR4在心肌缺血再灌注损伤中的作用.方法 雄性SD大鼠随机分为2组:假手术组(Sham组)、缺血再灌注组(IR组),每组36只,建立大鼠心肌缺血再灌注模型,按照不同的再灌注时间(0、0.5、1、24和8 h)处死动物.光镜和电镜观察心肌组织形态及超微结构改变.免疫组化检测心肌TLR4蛋白表达情况.实时定量逆转录聚合酶链反应定量心肌TLR4 mRNA表达水平.酶联免疫吸附试验测定心肌中肿瘤坏死因子-α(TNF-α)含量.结果 (1)Sham组心肌组织形态及超微结构改变不明显;IR组心肌损伤较重,缺血心肌恢复血液灌注8 h内,其病理学变化未见显著改善.(2)Sham组与IR组TLR4蛋白都有阳性表达,IR组TLR4表达增加,且以再灌注1 h最为明显(19.62±3.84,P＜0.01).(3)与Sham组比较,IR组心肌,TLR4 mRNA表达水平均出现不同程度上调,以再灌注1 h达到峰值[(4.03±0.85)×10-2,P＜0.01],而Sham组各时间点未见明显改变.(4)IR组心肌TNF-α水平高于各对应时间点Sham组(P均＜0.05),且心肌TLR4 mRNA表达与TNF-α呈正相关(r=0.728,P＜0.01).结论 心肌缺血再灌注早期,心肌TLR4表达迅速上调,TLR4的激活可能通过促进TNF-α等炎性因子的产生分泌增多来介导心肌缺血再灌注损伤.     

灯盏花素对缺血再灌注大鼠心肌JAK及STAT基因表达的影响

目的研究灯盏花素对大鼠心肌缺血再灌注损伤的保护作用与双面神激酶-信号转导及转录激活因子(JAK-STAT)信号转导途径的关系。方法 40只SD大鼠随机分为假手术组,模型组及灯盏花素Ⅰ组和灯盏花素Ⅱ组。灯盏花素组分别给予高、低剂量(25、50 mg·kg-1·d-1)灯盏花素腹腔注射,连续7 d,末次于冠脉结扎前1 h腹腔注射给药。假手术组和模型组腹腔注射等量生理盐水,采用结扎大鼠左冠状动脉前降支方法制备心肌缺血再灌注模型。缺血30 min、再灌注2 h后,采用免疫组化法测定JAK2蛋白的表达;RT-PCR法检测STAT1及STAT3 mRNA的表达。结果与假手术组相比,模型组心肌细胞JAK2蛋白表达和STAT1 mRNA表达显著增加(P<0.01),STAT3 mRNA表达显著减少(P<0.01);与模型组相比,灯盏花素组JAK2的蛋白表达和STAT1 mRNA的表达减少(P<0.05),STAT3 mRNA表达显著增加(P<0.01)。结论灯盏花素减轻缺血再灌注引起的心肌细胞凋亡,其作用可能与激活JAK-STAT信号通路有关,即通过降低JAK2蛋白表达和STAT1 mRNA的表达,增加STAT3 mRNA的表达有关。     

黄芩茎叶总黄酮对大鼠心肌缺血再灌注细胞凋亡的保护作用及机制

目的 观察黄芩茎叶总黄酮(SSTF)对大鼠心肌缺血再灌注损伤的保护作用.方法 40只SD大鼠随机分为假手术组(sham组)、缺血再灌注组(IR组)、SSTF组.用结扎大鼠左冠状动脉前降支方法制备心肌缺血再灌注损伤模型.缺血30 min、再灌注2h后,采用Annexinv/PI双染,流式细胞仪检测心肌细胞的凋亡情况,采用免疫组化技术检测心肌细胞STAT蛋白表达情况.结果 与sham组相比,IR组的心肌细胞的凋亡率明显增加(P＜0.01),并且STAT1蛋白表达增加(P＜0.01),STAT3蛋白表达减少(P＜0.01);与IR组相比,SSTF可明显降低心肌细胞的凋亡率(P ＜0.05,P＜0.01);心肌细胞的STAT1蛋白表达减少(P＜0.05,P＜0.01);STAT3蛋白表达增加(P＜0.05,P＜0.01).结论 SSTF可能通过下调STAT1蛋白和上调STAT3蛋白表达,对心肌缺血再灌注损伤时细胞凋亡有一定的防治作用.     

NDRG2在大鼠心肌缺血再灌注损伤中的表达

目的:观察大鼠心肌缺血或心肌缺血再灌注损伤(RMMI)时,心肌组织中N-Mcy下游调节基因(NDRG2)表达的变化。方法:将60只健康成年SD大鼠随机分为对照组、单纯缺血组和缺血/再灌注(I/R)组,每组5~6只。单纯缺血组:套扎冠脉,选取缺血3、6、12、24 h 4个时间点。再灌注组分别选择再灌注后6、12、24和48 h后获取心脏。结果:单纯缺血组各时间点NDRG2的表达与对照组相比无显著差异,NDRG2 mRNA和其蛋白表达的变化一致。再灌注组与对照组比较,随着时间的延长,NDRG2 mRNA的表达逐渐降低,在缺血12 h达到最低(P0.01),NDRG2蛋白的表达在缺血24 h达到最低(P0.01)。结论:单纯心肌缺血不引起NDRG2基因及其蛋白表达水平的变化,但再灌注损伤可下调心肌细胞中NDRG2的表达。     

代谢型谷氨酸受体1α在大鼠脑缺血再灌注损伤中的基因表达变化

目的　观察大鼠大脑中动脉闭塞 (MCAO)后再灌注不同时点代谢型谷氨酸受体 1α(mGluR1α)的蛋白与基因表达的变化 ,以探讨其在脑缺血再灌注损伤中的意义。方法　 4 8只SD大鼠随机分为假手术组及缺血 2h再灌注 1、3、6、12、2 4、4 8及 72h组 ,用免疫组织化学、逆转录 聚合酶链反应 (RT PCR)技术和HE染色检测各组mGluR1α的蛋白表达、mRNA转录水平及坏死神经元的计数。结果　各缺血再灌注组mGluR1α表达均高于假手术组 ,再灌注 1hmGluR1α的mRNA转录即有升高 ,6h达到高峰 ,mGluR1α蛋白表达从 3h开始增加 ,12h达高峰 ,与神经元损伤程度一致。结论　脑缺血再灌注可引起mGluR1α表达上调 ,且与神经元损伤程度平行 ,提示mGluR1α参与介导了局灶性脑缺血再灌注损伤。     

环氧合酶2基因在大鼠脑缺血再灌注损伤中的表达及意义

目的探讨局灶性脑缺血再灌注损伤过程中环氧合酶2基因的表达及其意义。方法采用栓线法制备大鼠大脑中动脉缺血再灌注损伤模型。随机分为8组:假手术组,缺血2h组,缺血再灌注3h、6h、12h、24h、48h、72h组,每组10只。评定神经功能损伤,HE染色观察脑组织形态学改变。Northern blot、Western blot和免疫组织化学染色方法检测脑组织环氧合酶2 mRNA和蛋白产物表达。结果神经功能缺损表现随缺血再灌注时间的延长而逐渐加重。缺血2h组环氧合酶2 mRNA和蛋白产物表达比假手术组明显增加(P<0.01),再灌注后表达逐渐增强,再灌注12h环氧合酶2的mRNA表达达高峰(0.92±0.30),再灌注24h环氧合酶2的蛋白产物表达达高峰(0.72±0.18),与其它组比较差异有显著性(P<0.01)。结论环氧合酶2基因在局灶性脑缺血再灌注损伤中的表达呈动态变化过程,环氧合酶2可能与缺血再灌注后迟发性神经细胞死亡有关。     

灯盏花素对大鼠缺血再灌注心肌细胞凋亡及STAT表达的影响

目的 观察灯盏花素对大鼠心肌缺血再灌注细胞凋亡和信号转导及转录激活因子(STAT)表达的影响,初步探讨其可能的作用机制.方法 采用结扎大鼠左冠状动脉前降支方法制备心肌缺血再灌注模型.将40只SD大鼠随机分为假手术组、缺血再灌注组,灯盏花素1组[25 mg/(kg,d)],灯盏花素2组[50 mg/(kg·d)].缺血30min、再灌注2h后,原位末端标记法测定组织中心肌细胞凋亡率,免疫组化SP法检测心肌组织中STAT蛋白的表达.结果 与假手术组相比,缺血再灌注组细胞凋亡率明显升高(P＜0.01),SP染色见STAT1蛋白表达显著增强(P＜0.05或＜0.01),但STAT3蛋白表达显著减少(P＜0.05或＜0.01);与缺血再灌注组相比,灯盏花素1、2组细胞凋亡率明显下降(P＜0.01),STAT1蛋白表达显著减少(P＜0.05或＜0.01),但STAT3蛋白表达显著增强(P＜0.05或＜0.01).结论 灯盏花素能够减轻缺血再灌注造成的心肌损伤,其机制可能与灯盏花素干预STAT蛋白表达,从而减少心肌细胞凋亡有关;STAT途径可能是灯盏花素抑制细胞凋亡的途径之一.     

Polyamine metabolism in rat myocardial ischemia-reperfusion injury

This study was focused on investigating the involvement of polyamine metabolism in the myocardial ischemia-reperfusion injury (MIRI) in an in vivo rat model. A branch of the descending left coronary artery was occluded for 30 min followed by 2 h, 6 h, 12 h, and 24 h reperfusion. Then the expression of spermidine/spermine N1-acetyltransferase (SSAT) and ornithine decarboxylase (ODC) and the concentrations of polyamines were assessed. It was found that the expression of SSAT and ODC were upregulated after reperfusion and the concentrations of spermidine and spermine were significantly decreased, while putrescine concentration was significantly increased. The results suggest that MIRI may cause disturbance of polyamine metabolism, and it may play a critical role in MIRI.     

Gossypol activates pancreatic polyamine catabolism in normal rats and induces acute pancreatitis in transgenic rats over-expressing spermidine/spermine N1-acetyltransferase

BACKGROUND: The male antifertility agent gossypol has been reported to induce spermidine/spermine N1-acetyltransferase (SSAT) in canine prostate cells. As SSAT is the rate-controlling enzyme in the catabolism of the polyamines and is involved in the development of acute pancreatitis in a recent transgenic rat model, we exposed normal and transgenic rats over-expressing SSAT to gossypol to evaluate its effect on pancreatic polyamine metabolism and organ integrity. METHODS: Pancreatic SSAT activity, polyamine pools, pancreatic histology and plasma 2-amylase activity were determined after different doses of gossypol. RESULTS: Gossypol increased pancreatic putrescine and decreased spermidine and spermine pools in normal rats accompanied by tissue oedema and significantly elevated plasma amylase activity. In transgenic rats, the drug strikingly induced SSAT, profoundly depleted the higher polyamines and caused distinct pancreatitis. The combination of gossypol at doses harmless to transgenic pancreas with an inhibitor of polyamine oxidase caused massive synergistic induction of SSAT, profound depletion of the polyamine pools and acute pancreatitis. CONCLUSIONS: The results indicate that gossypol induces pancreatitis through an activation of polyamine catabolism.     

Gossypol Activates Pancreatic Polyamine Catabolism in Normal Rats and Induces Acute Pancreatitis in Transgenic Rats Over-expressing Spermidine/Spermine N 1 -Acetyltransferase

Background: The male antifertility agent gossypol has been reported to induce spermidine/spermine N 1 -acetyltransferase (SSAT) in canine prostate cells. As SSAT is the rate-controlling enzyme in the catabolism of the polyamines and is involved in the development of acute pancreatitis in a recent transgenic rat model, we exposed normal and transgenic rats over-expressing SSAT to gossypol to evaluate its effect on pancreatic polyamine metabolism and organ integrity. Methods: Pancreatic SSAT activity, polyamine pools, pancreatic histology and plasma &#33 -amylase activity were determined after different doses of gossypol. Results: Gossypol increased pancreatic putrescine and decreased spermidine and spermine pools in normal rats accompanied by tissue oedema and significantly elevated plasma amylase activity. In transgenic rats, the drug strikingly induced SSAT, profoundly depleted the higher polyamines and caused distinct pancreatitis. The combination of gossypol at doses harmless to transgenic pancreas with an inhibitor of polyamine oxidase caused massive synergistic induction of SSAT, profound depletion of the polyamine pools and acute pancreatitis. Conclusions: The results indicate that gossypol induces pancreatitis through an activation of polyamine catabolism.     

Polyamine synthesis and transport inhibition in a human anaplastic thyroid carcinoma cell line in vitro and as xenograft tumors.

Polyamines are essential cellular components for neoplastic transformation and cell proliferation. Antineoplastic efforts that inhibit polyamine synthesis are insufficient to induce cytotoxicity, due to compensatory induction of polyamine transport. Treatment of an anaplastic human thyroid carcinoma cell line (DRO90-1) with a novel polymeric spermine conjugate (polyspermine; PSpm) caused in vitro cytotoxicity and inhibited the growth of xenograft tumors at low concentrations. Similar in vitro antineoplastic effects were noted with two other human anaplastic thyroid carcinoma cell lines. This coincided with inhibition of polyamine uptake and synthetic enzyme activities, with reduced ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAM-DC) but increased spermidine/spermine N1-acetyltransferase (SSAT) activities, as measured in DRO90-1 cells. In subsequent studies using these cells, PSpm was effective in reducing the intracellular levels of all polyamines in vitro, resulting in cytotoxicity that was not reversed by administration of extracellular polyamines. Low-dose PSpm inhibited tumor growth in vivo, but high doses of PSpm potentiated xenograft tumor growth. PSpm degradation products produced with in vivo treatment may be produced that function as substrates for polyamine biosynthesis. These studies suggest that polyamine metabolism inhibition is a viable target for antineoplastic therapy of anaplastic thyroid carcinoma, although the in vivo response to PSpm suggests that this agent will have limited clinical utility.     

Activation of polyamine catabolism in transgenic rats induces acute pancreatitis

Polyamines are required for optimal growth and function of cells. Regulation of their cellular homeostasis is therefore tightly controlled. The key regulatory enzyme for polyamine catabolism is the spermidine/spermine N(1)-acetyltransferase (SSAT). Depletion of cellular polyamines has been associated with inhibition of growth and programmed cell death. To investigate the physiological function SSAT, we generated a transgenic rat line overexpressing the SSAT gene under the control of the inducible mouse metallothionein I promoter. Administration of zinc resulted in a marked induction of pancreatic SSAT, overaccumulation of putrescine, and appearance of N(1)-acetylspermidine with extensive depletion of spermidine and spermine in transgenic animals. The activation of pancreatic polyamine catabolism resulted in acute pancreatitis. In nontransgenic animals, an equal dose of zinc did not affect pancreatic polyamine pools, nor did it induce pancreatitis. Acetylated polyamines, products of the SSAT-catalyzed reaction, are metabolized further by the polyamine oxidase (PAO) generating hydrogen peroxide, which might cause or contribute to the pancreatic inflammatory process. Administration of specific PAO inhibitor, MDL72527 [N(1),N(2)-bis(2,3-butadienyl)-1,4-butanediamine], however, did not affect the histological score of the pancreatitis. Induction of SSAT by the polyamine analogue N(1),N(11)-diethylnorspermine reduced pancreatic polyamines levels only moderately and without signs of organ inflammation. In contrast, the combination of N(1), N(11)-diethylnorspermine with MDL72527 dramatically activated SSAT, causing profound depletion of pancreatic polyamines and acute pancreatitis. These results demonstrate that acute induction of SSAT leads to pancreatic inflammation, suggesting that sufficient pools of higher polyamine levels are essential to maintain pancreatic integrity. This inflammatory process is independent of the production of hydrogen peroxide by PAO.     

Age-related changes in polyamine biosynthesis after fasting and refeeding

The effect of aging on ornithine decarboxylase (ODC) activity and polyamine biosynthesis in the proximal small intestine was studied in two groups of male Fisher 344 rats (young [4-month old] and aged [26- to 27-month old]) using a fasting and refeeding model. In control (nonfasted) rats, levels of polyamines (putrescine, spermidine and spermine) and ODC activity were significantly higher in aged compared with young rats. In aged rats, fasting significantly reduced the levels of putrescine by 41%, spermidine by 23%, and spermine by 11%; however, fasting had no effect on polyamine levels in young rats. ODC activity was decreased 75% in young and 50% in aged rats after fasting compared with the respective age-matched controls. Conversely, 2 h after reinstituting a chow diet increased ODC activity by 17-fold in young rats but only 8-fold in aged rats. Putrescine levels were also increased in both age groups after refeeding; however, similar to ODC activity, these increases were much less in aged rats. In addition, spermidine and spermine levels remained significantly depressed in the aged groups even after 24 h of refeeding. These findings suggest that the normal rigid control of gut polyamine biosynthesis and proliferation noted in young rats is markedly altered with aging.     

Role of polyamines in isoproterenol-induced cardiac hypertrophy: effects of alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase

DFMO is a selective irreversible inhibitor of ornithine decarboxylase (ODC), the initial enzyme in the polyamine biosynthetic pathway. DFMO was utilized to determine the role of polyamines in isoproterenol (ISO)-induced cardiac hypertrophy. Daily subcutaneous administration of 200 mg/kg of DFMO reduced cardiac putrescine levels but did not significantly alter the basal levels of spermidine or spermine, nor was normal cardiac growth affected. ISO-induced cardiac hypertrophy was accompanied by increased putrescine and spermidine levels but spermine was not significantly altered. DFMO reversed the ISO-induced increases in putrescine and inhibited or attenuated both the increases in spermidine content and the cardiac hypertrophy. Although normal ODC activity appears not to be necessary for the maintenance of basal levels of polyamines or for normal cardiac growth, sustained inhibition of ODC interferes with ISO-induced elevations of putrescine, spermidine and heart weight.     

Polyamine levels of human colorectal adenocarcinomas are correlated with tumor stage and grade

BACKGROUND AND AIMS: Cellular proliferation and differentiation are regulated by polyamines and their rate-limiting enzyme ornithine decarboxylase (ODC), both of which are correlated with tumor growth, but their role in differentiation is less clear. We investigated the correlation of ODC activity and polyamine levels with tumor stage and grade with respect to sample recruitment. PATIENTS AND METHODS: We determined ODC activity ([(14)C]CO(2) release), polyamines (HPLC), and histological staging and grading (TNM classification) of tissue samples from 64 patients with colorectal adenocarcinomas. RESULTS: We found the concentrations of putrescine, spermidine, and N(1)-acetyl-spermidine and the ODC activity in tumor tissue to be twice as high as in adjacent normal mucosa. A critical parameter affecting ODC activity was ischemic time, which significantly reduced ODC activity levels in tumors (threefold) and in the surrounding normal tissue (ninefold) when the ischemic period exceeded 1 h. By contrast, polyamine content was not affected by ischemia. Total polyamine and spermine concentrations were higher in T3 and T4 than in T2 tumors, but putrescine was higher in T4 than in T3 and T2 tumors. There were significantly higher levels of total polyamines and spermine in moderately differentiated (G2) than in poorly differentiated (G3) tumors. CONCLUSION: The lower spermidine/spermine ratio in G2 (0.44) compared with that in G3 (0.64) tumors suggests the involvement of the polyamines in colonic cell differentiation. Polyamine content is thus correlated with the tumor stage.     

Acute hypoxia increases ornithine decarboxylase activity and polyamine concentrations in fetal rat brain.

The cellular responses to hypoxia are poorly understood. To test the hypothesis that ornithine decarboxylase (ODC; L-ornithine carboxy-lyase; EC 4.1.1.17) activity and polyamine concentrations change in response to acute hypoxia, we performed the following studies. Pregnant Sprague-Dawley rats inspired various O2 concentrations (9-21%) for various time periods (0.5-48 h) from days 15 to 21 of gestation. In fetal brains we measured the activity of ODC, ODC mRNA, and polyamines. In response to 4-h acute mild hypoxia, ODC activity in fetal rat brain (cerebrum, cerebellum, and hippocampus) increased to 330-450% from control values (P < 0.001), after which it declined to control levels in 6-8 h. The 4-h ODC response varied inversely with inspired O2 concentration and was not mimicked by beta 2 agonist or blocked by beta 2-antagonist administration. The ODC response was associated with an increase in fetal brain putrescine concentration to 190% above control at 4-6 h (P < 0.01) and an increase in the polyamines spermidine and spermine to about 115% above control at 6-8 h. We also observed that ODC mRNA increased significantly after 2-4 h of hypoxia. ODC activity and polyamine concentrations appear to be useful enzymatic markers for fetal brain hypoxia. The magnitude and time course of the acute hypoxic ODC increase were similar to responses to extracellular signals that result in differentiation or cell growth. Thus, the well-defined and regulated ODC activity response may represent a protective mechanism in brain to hypoxia.     

Arterial injury-induced smooth muscle cell proliferation in rats is accompanied by increase in polyamine synthesis and level

Proliferation of smooth muscle cells (SMC), enhancement of polyamine biosynthesis and increase in polyamine level in response to deendothelialization in the rat aorta were studied. [3H]Thymidine incorporation into SMC in aortas denuded with a balloon catheter began 25 h after injury, and maximal incorporation occurred 33-37 h after injury. Afterwards, [3H]thymidine incorporation declined, approaching the baseline level, but was slightly higher than that of sham-operated controls until 14 days after injury. Intimal thickening started 7 days after injury, and peaked at 21 days. Prior to these proliferative changes in aortic SMC, a rapid and transient increase in ornithine decarboxylase (ODC) activity was observed within 8 h after injury. There was no significant difference in ODC activity between injured and intact aortas after 4 days. The levels of polyamines, putrescine, spermidine, and spermine increased and were maximal at 48 h after injury, 8.1, 3.4 and 1.4 times the control levels, respectively. Increased levels of polyamines, in particular spermidine, continued until 7 days after injury. These results suggest that the enhancement of polyamine synthesis and the increased polyamine content of the aorta play important roles in the proliferation of SMC and in the development of intimal thickening, particularly in the initial proliferative response of medial SMC after deendothelialization.