复方丹参滴丸对自发性高血压大鼠血管壁重建的干预及可能机制

目的 研究早期、长期辅助运用复方丹参滴丸对自发性高血压大鼠血管壁重建的干预及可能机制.方法 10周龄自发性高血压大鼠48只随机分成6组:治疗前对照组、阴性对照组、络活喜治疗组、复方丹参滴丸后期治疗组、复方丹参滴丸早期治疗组和复方丹参滴丸长期治疗组,检测胸主动脉壁厚度和血管壁平滑肌细胞增长率,以及基质金属蛋白酶2、内皮素1和层粘连蛋白相对表达水平.结果 与复方丹参滴丸早期治疗组比,复方丹参滴丸长期治疗组血管平滑肌细胞增长率明显减少,而复方丹参滴丸后期治疗组则明显增加.在降压治疗(络活喜)基础上加用复方丹参组其内皮素1、基质金属蛋白酶2表达均有不同程度减少,而层粘连蛋白增加,且出现时间在血管平滑肌细胞增长率变化之前.结论 在有效降压治疗基础上早期、长期联合运用复方丹参滴丸可能通过产生生物学效应(基质金属蛋白酶2和内皮素1表达减少,层粘连蛋白表达增加)来遏制因此而产生的力学效应(血管平滑肌细胞增长率),从而改善血管壁的重建和增厚.     

老龄大鼠脑缺血再灌注损伤与明胶酶系基因表达的关系

目的研究老龄大鼠脑缺血再灌注不同时期微血管基底膜损伤与明胶酶系基因表达的关系。方法制备SD雄性大鼠局灶性脑缺血再灌注模型,将56只青年大鼠分为青年假手术组、青年模型组,56只老龄大鼠分为老龄假手术组、老龄模型组,其中青年与老龄模型组又分缺血3h和再灌注6、12、24h,3、6天时间点。观察脑微血管结构基底膜病理形态变化和明胶酶系的基因表达变化。结果老龄假手术组大鼠脑皮质微血管结构基本正常,老龄模型组与同时间点青年模型组比较病理损伤较重。随再灌注时间的延长,基质金属蛋白酶-2(MMP-2)mRNA表达递增,基质金属蛋白酶-9(MMP-9)mRNA和金属蛋白酶组织抑制-1(TIMP-1)mRNA表达呈先增强后降低趋势。与青年模型组相同时间点比较,老龄模型组MMP-2、MMP-9mRNA表达水平增强;TIMP-1mRNA仅在再灌注24h表达水平降低,差异均有显著性。结论随着增龄,大鼠脑微血管基底膜损伤改变与MMPmRNA、TIMPmRNA的变化有关。老龄大鼠较青年大鼠病理损伤严重。     

广谱基质金属蛋白酶抑制剂多西环素对高血压大鼠主动脉结构的影响

目的利用多西环素的非特异性基质金属蛋白酶抑制剂特性,研究该药对高血压性主动脉重塑的影响。方法80只7周龄雄性卒中易感型自发性高血压(SHR-SP)大鼠随机分为药物干预组和对照组,同时饲养同周龄雄性WKY大鼠。药物干预组每天经自由饮水给予多西环素30mg/(kg.d)。观察6个月后处死动物留取主动脉,一部分组织用于制备石蜡切片并进行HE、维多利亚蓝(弹力纤维特异性染色)和vonKossa银(异常钙沉积染色)染色,另一部分组织用于交联胶原测定和明胶酶谱分析。结果两组高血压大鼠的主动脉内膜周长、外膜周长和血管中膜面积差异无显著性。采用明胶酶谱法,在各组均未检测到基质金属蛋白酶9活性;与对照组比较,药物干预组基质金属蛋白酶2活性显著降低(2.43±0.14比3.15±0.23,P0.05)。维多利亚蓝动脉弹力纤维染色分析显示,与对照组比较,药物干预组弹力纤维占中膜面积百分比显著降低[3.46%±1.62%比5.72%±3.87%,P0.05]。药物干预组交联胶原浓度与对照组比差异无统计学意义(26.4±7.0mg/g比28.0±8.7mg/g,P0.05)。与对照组比较,药物干预组钙沉积占中膜面积百分比虽无统计学差异,但存在降低的趋势[0.688%±0.718%比0.960%±0.999%,P=0.177]。结论多西环素可以抑制SHR-SP主动脉中基质金属蛋白酶2活性,但在血压没有得到有效控制的前提下会加重高血压性主动脉硬化的程度。     

广谱基质金属蛋白酶抑制剂多西环素对血压大鼠主动脉结构的影响

目的利用多西环素的非特异性基质金属蛋白酶抑制剂特性,研究该药对高血压性主动脉重塑的影响。方法80只7周龄雄性卒中易感型自发性高血压(SHR-SP)大鼠随机分为药物干预组和对照组,同时饲养同周龄雄性WKY大鼠。药物干预组每天经自由饮水给予多西环素30mg/(kg.d)。观察6个月后处死动物留取主动脉,一部分组织用于制备石蜡切片并进行HE、维多利亚蓝(弹力纤维特异性染色)和vonKossa银(异常钙沉积染色)染色,另一部分组织用于交联胶原测定和明胶酶谱分析。结果两组高血压大鼠的主动脉内膜周长、外膜周长和血管中膜面积差异无显著性。采用明胶酶谱法,在各组均未检测到基质金属蛋白酶9活性;与对照组比较,药物干预组基质金属蛋白酶2活性显著降低(2.43±0.14比3.15±0.23,P<0.05)。维多利亚蓝动脉弹力纤维染色分析显示,与对照组比较,药物干预组弹力纤维占中膜面积百分比显著降低[3.46%±1.62%比5.72%±3.87%,P<0.05]。药物干预组交联胶原浓度与对照组比差异无统计学意义(26.4±7.0mg/g比28.0±8.7mg/g,P>0.05)。与对照组比较,药物干预组钙沉积占中膜面积百分比虽无统计...     

易卒中型肾血管性高血压大鼠脑组织及血清中基质金属蛋白酶9的表达

目的 探讨易卒中型肾血管性高血压大鼠(RHRSP)脑组织及血清中基质金属蛋白酶9(MMP-9)的表达及在高血压脑卒中发生中的作用.方法 健康雄性SD大鼠50只随机分成RHRSP组(35只)和假手术组(15只).RHRSP组采用双肾双夹法造模,鼠尾测压仪测定收缩压.根据Longa5评分法和病理学结果再将RHRSP组分为脑...     

阻断清道夫受体AⅠ对巨噬细胞源泡沫细胞基质金属蛋白酶及其组织抑制剂表达的影响

为探讨巨噬细胞源泡沫细胞基质金属蛋白酶及其组织抑制剂的表达及活性与清道夫受体AⅠ的关系，应用油红O染色、高效液相色谱法检测巨噬细胞的泡沫化，逆转录聚合酶链反应检测细胞清道夫受体AⅠ的表达，Westem blot明胶酶谱法观测巨噬细胞泡沫化后阻断清道夫受体AⅠ对THP—1细胞基质金属蛋白酶2、基质金属蛋白酶9、组织型基质金属蛋白酶抑制剂1及组织型基质金属蛋白酶抑制剂2表达的影呐。结果发现，THP—1细胞在佛波酯处理24h后有清道夫受体AⅠ的表达，清道夫受体AⅠ反义寡核苷酸及其抗体能显著降低基质金属蛋白酶2和基质金属蛋白酶9的蛋白表达和活性，并增加组织型基质金属蛋白酶抑制剂1和组织型基质金属蛋白酶抑制剂2的表达。结果提示，阻断清道夫受体AⅠ有助于基质金属蛋白酶与组织型基质金属蛋白酶抑制剂的平衡维持，从而抑制细胞外基质的降解。     

罗格列酮对2型糖尿病大鼠大血管病变的防治作用及其分子机制

目的探讨基质金属蛋白酶9表达和活化与2型糖尿病大鼠大血管病变的关系以及罗格列酮抗动脉粥样硬化的分子机制。方法应用高脂饲料加小剂量链脲佐菌素建立2型糖尿病大鼠模型,用含明胶十二烷基硫酸钠—聚丙烯酰胺凝胶电泳方法检测基质金属蛋白酶9活性,用逆转录聚合酶链反应检测基质金属蛋白酶9 mRNA的表达,并观察罗格列酮治疗48、和12周基质金属蛋白酶9的表达及活性的变化。结果糖尿病组大鼠主动脉基质金属蛋白酶9的活性是正常大鼠的1.37倍,且随着糖尿病病程的延长而增强,分别是正常组大鼠的1.69、2.25和2.92倍,基质金属蛋白酶9 mRNA的表达呈增高趋势,分别是正常组的1.15、1.30、1.45和1.99倍;罗格列酮治疗后基质金属蛋白酶9的活性分别比模型组降低11.56%、37.73%和48.60%,基质金属蛋白酶9 mRNA表达量分别比模型组降低26.80%、27.16%和46.46%。结论在2型糖尿病大血管病变形成过程中,伴有基质金属蛋白酶9表达和活性的变化,罗格列酮防治糖尿病大血管病变的机制与抑制基质金属蛋白酶9基因表达和活性有关。     

基质金属蛋白酶及其抑制因子在脑外伤大鼠脑水肿区表达的研究

1目的 脑外伤后继发脑水肿是血管源性脑水肿,血管基底膜损坏可能在血管源性脑水肿中起重要作用.明胶酶A(gelatinase A,又称MMP-2)和明胶酶B(celatinase B,又称MMP-9)可降解血管基底膜的主要成分--Ⅳ型胶原.我们用逆转录定量PCR方法研究大鼠脑外伤后水肿区脑组织基质金属蛋白酶(tissue matrix metalloproteinases,MMPs)及其抑制因子(tissue inhibiter of matrix metalloproteinases,TIMPs)基因表达情况,探讨其与脑水肿发生机制的关系.     

大鼠脑出血后血管内皮生长因子和基质金属蛋白酶9的表达及七叶皂苷钠的影响

目的探讨血管内皮生长因子和基质金属蛋白酶9在脑出血后的作用及七叶皂苷钠的影响。方法85只大鼠随机分为脑出血模型组(20)、治疗组A(20)、治疗组B(20)、假手术组(20)和正常对照组(5),采用胶原酶复制大鼠基底节区脑内血肿模型,通过免疫组织化学动态测定不同时间点(6 h、24 h、48 h和96 h)鼠脑内血肿周围脑组织中血管内皮生长因子和基质金属蛋白酶9的表达;并同时检测七叶皂苷钠干预后两者在相应时间点的动态变化。结果血管内皮生长因子和基质金属蛋白酶9在脑出血模型组出血后6 h表达明显增加,分别为12.67±1.50和9.27±1.28,24~96 h显著增加且均处于高峰(P<0.01);在出血后6~96 h两者的表达呈正相关,相关系数为0.479(P<0.01)。在七叶皂苷钠治疗组血管内皮生长因子、基质金属蛋白酶9的表达量明显受到抑制(特别是治疗B组抑制效果更明显),量效关系呈负相关其决定系数分别为0.107和0.083。结论1.脑出血后血管内皮生长因子的表达水平提高可能有协同诱导基质金属蛋白酶9的表达作用。2.七叶皂苷钠可能通过抑制基质金属蛋白酶9和血管内皮生长因子的相关途径发挥抗脑水肿作用。     

氧化型低密度脂蛋白对大鼠血管平滑肌细胞基质金属蛋白酶-2和9表达的影响

为探讨氧化型低密度脂蛋白致动脉粥样硬化的作用是否与基质金属蛋白酶表达活性改变有关,应用Northern blot、Dot blot、Westorn blott和明胶酶图分析方法观察氧化型低密度脂蛋白对体外培养的大鼠血管平滑肌细胞表达基质金属蛋白酶－2和9的影响。结果显示,10mg/L氧化型低密度脂蛋白作用于血管平滑骨细胞24h,可明显增强基质金属蛋白酶－2和9mRNA的表达、蛋白分泌和酶的活性,高浓度的氧化型低密度脂蛋白对基质金属蛋白酶－2和9表达的影响不同,氧化型低密度脂蛋白浓度为50mg／L时,基质金属蛋白酶－9表达活性仍然高于对照细胞,但于10mg／L氧化型低密度脂蛋白的作用强度无显著差别;相同条件下,基质金属蛋白酶－2的基因表达和蛋白分泌明显降低。以上结果提示,氧化型低密度脂蛋白可诱导血管平滑肌细胞基质金属蛋白酶－2和9的表达,并可促进细胞外基质降解。     

Impaired extracellular matrix degradation in aortic vessels of cirrhotic rats

BACKGROUND/AIMS: Thinning of the vascular wall occurs in conductance vessels of cirrhotic rats. Increased nitric oxide synthase (NOS) activity has been involved in the pathogenesis of this phenomenon. Therefore, we assessed the NO-regulated cell signaling pathways participating in vascular remodeling in cirrhosis. METHODS: Aortas were obtained from 15 control and 15 cirrhotic rats. Phosphorylated p38 MAPK and ERK1/2 were used to evaluate the activation of cell MAPK signaling pathways. Extracellular matrix (ECM) turnover was estimated by measuring matrix metalloproteinases (MMPs) activity and protein expression of collagen IV, MMP-2, MMP-9 and tissue inhibitor of MMPs (TIMP)-2. Thereafter, 12 control and 12 cirrhotic rats received Nomega-nitro-L-arginine-methyl-ester or vehicle daily for 11 weeks. RESULTS: Cirrhotic vessels showed a reduction in ERK1/2 phosphorylation, lower MMP activity, decreased MMPs expression and higher collagen IV and TIMP-2 abundance, compared to control rats. Chronic NOS inhibition normalized ERK1/2 phosphorylation and MMPs activity, increased MMPs abundance and decreased TIMP-2 expression in cirrhotic rats. CONCLUSIONS: Vascular remodeling in cirrhotic rats is mediated by down-regulation of cell growth and impaired ERK1/2 activation and subsequent imbalance of ECM turnover. These results further stress the importance of vascular NO overactivity in the reduction of vascular wall thickness in cirrhosis.     

Changes in vascular wall production of prostacyclin and thromboxane A2 in spontaneously hypertensive rats during maturation and the concomitant development of hypertension

The purpose of this study was to clarify how the metabolism of vascular prostacyclin (PGI2) and thromboxane (TX) A2 in spontaneously hypertensive rats (SHR) is involved in aging and development of hypertension. We removed the aortic walls from 5-week-old and 20 to 25-week-old SHR and age-matched Wistar Kyoto rats (WKY). At 5 weeks of age, there was no significant difference in basal and maximal (arachidonic acid 0.1 mM) 6-keto-PGF1 alpha production between SHR and WKY, but the TXB2 generation in the SHR aortic wall was markedly enhanced as compared with that in WKY. At 20 to 25 weeks of age, the SHR aortic wall synthesized about 1.5 times more 6-keto-PGF1 alpha in the basal condition and twice as much as in the maximal condition as did the WKY wall. However there was no significant difference in TXB2 production between SHR and WKY. Age-dependent increase of vascular 6-keto-PGF1 alpha was greater in SHR than in WKY. Moreover, the maximal/basal 6-keto-PGF1 alpha production ratio increased with age in SHR, but not in WKY. The synthesis of vascular TXB2 was enhanced with age in WKY, but did not change with age in SHR. These data suggest that not only the enhanced basal generation of vascular 6-keto PGF1 alpha but also a much greater reservoir of 6-keto-PGF 1 alpha synthesis in SHR was induced by both hypertension and maturity. The increased production of vascular TXB2 in young SHR may affect the development of hypertension.     

Estrogen replacement reduces age-associated remodeling in rat mesenteric arteries

Estrogen replacement therapy significantly decreases the incidence of cardiovascular disease in postmenopausal women. In aging, there is an increase in vascular stiffness along with a decrease in matrix metalloproteinase (MMP) activity. Our hypothesis was that estrogen replacement would increase MMPs and therefore reduce the vascular stiffness that is associated with aging. Female Sprague-Dawley rats were implanted with a placebo or 17ss-estradiol-containing pellet (0.5 mg/pellet, 60-day release) at 10 months of age (n=6, each). Six young rats (3 months old) were also studied. After a 2-month exposure to the pellet, mesenteric arteries were studied on a pressurized arteriograph system. Distensibility and wall thickness were measured in response to stepwise increases in intraluminal pressure in Ca(2+)-free physiological saline solution buffer with papaverine (10(-4) mol/L). In response to increasing pressure, aged placebo rats exhibited a significant decrease in distensibility compared with young rats (P<0.05) that was accompanied by an increase in wall thickness (P<0.05). Conversely, estrogen replacement increased distensibility and decreased wall thickness in aged rats (old estrogen-replaced versus old placebo, P<0.05). Zymography data indicated that MMP-2 activity decreased in aging but was increased by estrogen replacement. In summary, estrogen replacement in aging female rats reduces age-associated vascular remodeling.     

RECS1 is a negative regulator of matrix metalloproteinase-9 production and aged RECS1 knockout mice are prone to aortic dilation.

BACKGROUND: RECS1 is a mechanical stress responsive gene and RECS1 knockout (KO) mice (older than 14 months) are prone to cystic medial degeneration (CMD). The present study was designed to assess whether RECS1 KO mice have altered gelatinase (matrix metalloproteinase (MMP)-2 and MMP-9) levels and whether they are prone to aortic dilation. METHODS AND RESULTS: Aortic and plasma gelatinase levels in RECS1 KO and wild-type (WT) mice were assessed by gelatin zymography and Western blot analysis. Pro-MMP-9 (in the aorta), neutrophil gelatinase-associated lipocalin/MMP-9 complex (NGAL-MMP-9, in plasma), and active-MMP-9 protein levels were more abundant in KO mice throughout adulthood compared with WT mice. Aortic MMP-2, aortic MMP-9, and plasma MMP-9 activation increased with age, even though the aortic pro-MMP-9, plasma NGAL-MMP-9, aortic and plasma pro-MMP-2 production decreased: this was true both for the WT and KO animals. Aortic pro-MMP-2, aortic active-MMP-2, and plasma pro-MMP-2 protein levels were higher in the aged KO mice, but they were lower in the young KO mice than those in WT mice. Thoracic aortic dilation was observed only in the aged KO mice. In situ zymographic experiments confirmed that the increased aortic gelatinase activities were associated with CMD and aortic dilation observed in the aged KO mice. CONCLUSIONS: RECS1 negatively regulates aortic MMP-9 production and knocking out RECS1 induces susceptibility to aortic dilation as well as CMD in the aged mice. The present study suggests that RECS1 plays protective roles in vascular remodeling. We speculate that inhibiting unfavorable deposition and extracellular matrix degradation are both important for prevention and treatment of aneurysms.     

Alterations in vascular matrix metalloproteinase due to ageing and chronic hypertension: effects of endothelin receptor blockade

OBJECTIVE: To determine the effects of age and dual endothelin (ET)A/ETB receptor antagonism (bosentan) on aortic matrix metalloproteinase (MMP) abundance and tissue inhibitor of metalloproteinase (TIMP) expression in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). METHODS: Male SHR and control WKY rats were randomly assigned to receive placebo or bosentan (100 mg/kg per day) for 3 months. Animals were killed under terminal anaesthesia at either 20 weeks (adult) or 17-20 months (senescent). Aortic gelatinase activity was determined by zymography, whereas MT-1 MMP and TIMP-1 expression were assessed by immunoblotting. RESULTS: In WKY rats, aortic MMP-2 but not proMMP-2 activity was 3.6-fold higher (P < 0.02) in the senescent compared with the adult group. TIMP-1 (twofold) and MT-1 MMP (3.8-fold) expression increased (P < 0.05) with age in the WKY groups. Short-term hypertension (adult SHR versus adult WKY) increased MMP-2 to 74.7 +/- 14.1 from 18.9 +/- 3.5 arbitrary units (AU) (P = 0.0012), but did not alter proMMP-2 activity. This increased further on progression to chronic hypertension (117.4 +/- 12.2 versus 74.7 +/- 14.1 AU; P < 0.02). Bosentan decreased MMP-2 (78.9 +/- 3.8 versus 117.4 +/- 12.2 AU; P = 0.014) and proMMP-2 activity (P < 0.006) in the senescent SHR group. CONCLUSION: Ageing and the development/progression of hypertension are associated with increased MMP-2 activity in the aorta, which is consistent with ongoing remodelling of the vasculature. However, the underlying mechanisms regulating MMP-2 abundance in ageing and hypertension appear to be divergent, as MT-1 MMP expression is differentially altered. Dual ETA/ETB receptor antagonism did not alter the age-dependent increase in aortic MMP activity in normotensive rats. However, bosentan decreased pro and active MMP-2 activity in senescent SHR rats, indicating that ET modulates late events in vascular remodelling in hypertension.     

The role of the matrix metalloproteinases during in vitro vessel formation

Matrix metalloproteinases (MMPs) constitute a large family of extracellular matrix degrading proteases implicated in a number of physiological and pathological processes, including angiogenesis. However, the relative importance of the individual MMPs in vessel formation is poorly understood. Using the three-dimensional rat aortic model, the role of the MMPs in angiogenesis in vitro was investigated both by the use of synthetic MMP inhibitors, and by a study of the expression of nine MMPs and three of their endogenous inhibitors (the TIMPs) during vessel formation. Inhibition of microvessel growth in this model by the MMP inhibitor Marimastat demonstrated the requirement of the MMPs for angiogenesis in both collagen and fibrin matrices (half-maximal inhibition at 5 and 80 nM, respectively). The profile of MMP expression was seen to be modified by both matrix composition and exogenous growth factors. For example, whilst the gelatinase MMP-2 and stromelysin MMP-3 were present at high levels in fibrin culture, the stromelysin MMP-11 and membrane-type-1-MMP were more highly expressed during vessel formation in collagen. The angiogenic basic fibroblast growth factor (bFGF) upregulated the expression of the gelatinases (MMP-2 and MMP-9), the stromelysins (MMP-3, MMP-10 and MMP-11) and the interstitial collagenase MMP-13, whereas vascular endothelial growth factor (VEGF) led to a marked increase in expression of MMP-2 only. Together, the environment-dependent upregulation in expression of a number of MMPs during angiogenesis, and the total inhibition of vessel growth observed at nanomolar concentrations of synthetic MMP inhibitors, suggests a major collective role of these enzymes in angiogenesis, and provides a basis for further development of MMP inhibitors for anti-angiogenic therapy.     

Host metalloproteinases in Lyme arthritis.

OBJECTIVE: To assess the role of matrix metalloproteinases (MMPs) in cartilage and bone erosions in Lyme arthritis METHODS: We examined synovial fluid from 10 patients with Lyme arthritis for the presence of MMP-2, MMP-3, MMP-9, and "aggrecanase" activity using gelatinolytic zymography and immunoblot analysis. We developed an in vitro model of Lyme arthritis using cartilage explants and observed changes in cartilage degradation in the presence of Borrelia burgdorferi and/or various protease inhibitors. RESULTS: Synovial fluid from patients with Lyme arthritis was found to contain at least 3 MMPs: gelatinase A (MMP-2), stromelysin (MMP-3), and gelatinase B (MMP-9). In addition, there was evidence in 2 patients of "aggrecanase" activity not accounted for by the above enzymes. Infection of cartilage explants with B. burgdorferi resulted in induction of MMP-3, MMP-9, and "aggrecanase" activity. Increased induction of these enzymes by B. burgdorferi alone was not sufficient to cause cartilage destruction in the explants as measured by glycosaminoglycan (GAG) and hydroxyproline release. However, addition of plasminogen, which can act as an MMP activator, to cultures resulted in significant GAG and hydroxyproline release in the presence of B. burgdorferi. The MMP inhibitor batimastat significantly reduced the GAG release and completely inhibited the collagen degradation. CONCLUSION: MMPs are found in synovial fluids from patients with Lyme arthritis and are induced from cartilage tissue by the presence of B. burgdorferi. Inhibition of MMP activity prevents B. burgdorferi-induced cartilage degradation in vitro.     

Essential role for vascular gelatinase activity in relaxin-induced renal vasodilation, hyperfiltration, and reduced myogenic reactivity of small arteries

During pregnancy, relaxin stimulates nitric oxide (NO)-dependent renal vasodilation, hyperfiltration and reduced myogenic reactivity of small renal arteries via the endothelial ETB receptor subtype. Our objective in this study was to elucidate the mechanisms by which relaxin stimulates the endothelial ETB receptor/NO vasodilatory pathway. Using chronically instrumented conscious rats, we demonstrated that a specific peptide inhibitor of the gelatinases MMP-2 and -9, cyclic CTTHWGFTLC (cyclic CTT), but not the control peptide, STTHWGFTLS (STT), completely reversed renal vasodilation and hyperfiltration in relaxin-treated rats. Comparable findings were observed with a structurally different and well-established, general antagonist of MMPs, GM6001. In contrast, phosphoramidon, an inhibitor of endothelin-converting enzyme, did not significantly change the renal vasodilatory response to relaxin administration. When small renal arteries were incubated with either of the general MMP inhibitors, GM6001 or TIMP-2 (tissue inhibitor of MMP), or with the specific gelatinase inhibitor, cyclic CTT, the reduced myogenic reactivity of these blood vessels from relaxin-treated nonpregnant and midterm pregnant rats was totally abolished. Moreover, a neutralizing antibody specific for MMP-2 completely abrogated the reduced myogenic reactivity of small renal arteries from relaxin-treated nonpregnant and midterm pregnant rats. In contrast, phosphoramidon did not significantly affect the reduction in myogenic reactivity. Using gelatin zymography, we showed increased pro and active MMP-2 activity in small renal arteries from relaxin-treated nonpregnant and midterm pregnant rats relative to the control animals. Thus, inhibitors of MMPs in general and of gelatinases in particular reverse the renal vascular changes induced by pregnancy or relaxin administration to nonpregnant rats. Finally, the typical reduction in myogenic reactivity of small renal arteries from relaxin-treated nonpregnant rats was absent in ETB receptor-deficient rats, despite an increase in vascular MMP-2 activity. These results indicate an essential role for vascular gelatinase, which is in series with, and upstream of, the endothelial ETB receptor/NO signaling pathway in the renal vasodilatory response to relaxin and pregnancy.