The mode of action of prostaglandin E2, F2 alpha and prostacyclin on vesicourethral smooth muscle

Interactions of prostaglandin E2 (PGE2), F2 alpha (PGF2 alpha) and prostacyclin (PGI2) with Ca2+ on the isometric contraction of rabbit detrusor muscle strips were studied using two types of Ca2+ antagonists of different mechanisms of action: verapamil and sodium nitroprusside (NP). The effects of PGI2 on vesicourethral smooth muscle and their relationship with cholinergic, adrenergic receptors and nervous activity were also investigated. PGE2 and F2 alpha (3 X 10(-8) to 3 X 10(-5) M) caused dose-dependent contraction of the strips. Pretreatment of the strips with verapamil (10(-7) to 10(-5)M) significantly inhibited PGs-induced contraction in a dose-dependent manner, whereas NP(10(-7) to 10(-5)M) failed to suppress the contraction. Relaxation of the preparations once contracted by PGE2 and F2 alpha (3 X 10(-6)M) was induced completely by addition of verapamil (10(-5)M), and incompletely by NP(10(-5) to 10(-3)M). Washing of the strips with Ca2+-free solution containing 0.01 mM EGTA completely eliminated spontaneous activity and diminished basal tension, but replenishment of Ca2+ (0.5 to 10 mM) to the medium caused dose-related contraction and spontaneous activity of the strips. Addition of PGE2 and F2 alpha to the Ca2+-free medium enhanced Ca2+-induced contraction and spontaneous activity during Ca2+ replenishment, which were significantly inhibited by pretreatment with verapamil (10(-7) to 10(-5)M) in a dose-dependent manner, but not affected by NP (10(-7) to 10(-5)M). In Ca2+-free medium containing 0.1 mM EGTA, PGE2 and F2 alpha caused a slight degree of tension increase of the strips dose-dependently at the higher concentration exceeding 3 X 10(-6)M. PGI2 (10(-9) to 3 X 10(-4)M) caused dose-dependent contraction of the strips from the bladder body, base and the urethra. The contractile action of PGI2 was greatest on the bladder body, less on the base and minimal on the urethra. The effect of PGI2 was less potent than those of PGE2 and F2 alpha. The PGI2-induced contraction was slow in onset, short lasting, and not affected by pretreatment with phentolamine, propranolol, atropine, hexamethonium, hemicholinium-3 and tetrodotoxin. The interactions of PGI2 with Ca2+ were similar to those of PGE2 and F2 alpha.(ABSTRACT TRUNCATED AT 400 WORDS)     

前列腺素E1对血吸虫病家兔门静脉平滑肌细胞增殖的影响

目的 观察血吸虫病家兔门静脉高压症形成过程中,静脉应用前列腺素E1对门静脉血管平滑肌细胞(VSMC)增殖的影响及可能机制.方法 血吸虫尾蚴皮肤敷贴法感染家兔,构建门静脉高压模型,其中7只在感染尾蚴后60 d开始耳缘静脉给予PGEI(2.5μg/kg体重).至150 d透射电镜比较门静脉VSMC超微结构变化,Western blot和免疫组织化学分别检测门静脉血小板衍生生长因子B(PDGF-B)表达水平和表达部位.结果 血吸虫病家兔门静脉中膜增厚,VSMC活化增殖,PDGF-B表达增强并集中在中膜平滑肌层.外源性PGE1可以抑制VSMC增殖;显著降低门静脉中膜厚度[(76.35±11.41)μm比(118.29±36.52)μm,P《0.01]和PDGF-B[(3.63±1.39)比(6.64±1.95),P《0.05]表达.结论 VSMC增殖是血吸虫病家兔门静脉高压血管病变的重要环节.PGE1可以有效地抑制血吸虫家兔门静脉VSMC增殖,抑制PDGF-B表达可能是其中机制之一.     

Protective effect of prostaglandin E2 receptors EP2 and EP4 in alloimmune response in vivo

Prostaglandin E2 (PGE2) is produced during inflammatory responses mediating a variety of both innate and adaptive immune responses through 4 distinct receptors: EP1 to EP4. The use of gene-targeted mice and selective agonists/antagonists responsible for each receptor has gradually revealed that each receptor plays a unique and important role in various disease conditions. In addition, PGE2 is known to have some immunosuppressive properties. In this study, we investigated the role of PGE2 receptors by examining the therapeutic efficacy of highly selective receptor agonists on the alloimmune response in vivo. We used a fully major histocompatibility complex (MHC)-mismatched murine cardiac transplantation model. C57BL/6 cardiac allografts were heterotopically transplanted into BALB/c recipients. We treated mice with a highly selective agonist for each EP receptor. EP2 and EP4 agonists significantly prolonged allograft survival compared with controls. In particular, the EP4 agonist was more effective than the EP2 agonist in the inhibition of acute allograft rejection. In conclusion, PGE2 receptors merit further study as novel therapeutics for clinical transplantation.     

Time-dependent effect of prostaglandin E2 inhalation on airway responses to bronchoconstrictor agents in normal subjects.

Studies were performed to investigate whether hyperresponsiveness of the airways could be induced in normal subjects by inhalation of prostaglandin E2 (PGE2). During the initial bronchodilator phase of PGE2 action the bronchoconstrictor effect of inhaled histamine was significantly antagonised. When bronchoconstrictor challenges were started shortly after the end of the bronchodilator response to PGE2, however, significant enhancement of the effects of both inhaled histamine and methacholine occurred. It was predominantly sensitivity to these agents that was increased, with a parallel shift of the dose-response curves towards increased bronchoconstriction. Thus PGE2 may be protective in the acute phase of a bronchoconstrictor challenge, but in a chronic inflammatory condition its net effect may be a balance between this beneficial action and a non-specific potentiation of the activity of bronchoconstrictor agents.     

Effect of local prostaglandin E2 on periosteum and muscle in rabbits

We assessed the target tissue for the stimulatory effect of prostaglandin E₂ (PGE₂) on bone formation previously observed during fracture healing. PGE₂ was infused into tibial periosteal tissue in the right leg of 7 rabbits and into the anterior tibial muscle in the right leg of 7 other rabbits for 6 weeks. Solvent solution was infused into the left leg. PGE₂ infusion at the periosteum caused the formation of primitive woven bone with large amounts of connective tissue; solvent infusion caused small amounts of normal periosteal bone formation. In the neighboring cortical bone, remodeling was increased after PGE₂ infusion compared to solvent infusion. In the muscle, PGE₂ infusion caused the formation of connective tissue with small amounts of woven bone. Thus, the major effects of PGE₂ infusion at the site of the periosteum was the formation of primitive woven bone and in muscles the formation of connective tissue.     

Effect of local prostaglandin E2 on periosteum and muscle in rabbits.

We assessed the target tissue for the stimulatory effect of prostaglandin E2 (PGE2) on bone formation previously observed during fracture healing. PGE2 was infused into tibial periosteal tissue in the right leg of 7 rabbits and into the anterior tibial muscle in the right leg of 7 other rabbits for 6 weeks. Solvent solution was infused into the left leg. PGE2 infusion at the periosteum caused the formation of primitive woven bone with large amounts of connective tissue; solvent infusion caused small amounts of normal periosteal bone formation. In the neighboring cortical bone, remodeling was increased after PGE2 infusion compared to solvent infusion. In the muscle, PGE2 infusion caused the formation of connective tissue with small amounts of woven bone. Thus, the major effects of PGE2 infusion at the site of the periosteum was the formation of primitive woven bone and in muscles the formation of connective tissue.     

Misoprostol induces relaxation of human corpus cavernosum smooth muscle: comparison to prostaglandin E1

Prostaglandin E1 (PGE1) relaxes trabecular smooth muscle by interacting with specific G-protein coupled receptors on human corpus cavernosum smooth muscle and increasing intracellular synthesis of cAMP. Misoprostol (Cytotec), is an oral prostaglandin E analogue. The purpose of this study was to compare the functional activity of misoprostol with PGE1 in human corpus cavernosum and cultured human corpus cavernosum smooth muscle cells. Misoprostol, misoprostol free acid or PGE1 induced dose-dependent relaxations in strips of human corpus cavernosum. At concentrations greater than 10(-6) M, tissue recontraction was observed with all three agents. This was abrogated by pretreatment with the thromboxane A2 receptor antagonist SQ29,548. From these observations, we conclude that misoprostol is activated by human corpus cavernosum in situ and relaxes phenylephrine-precontrated tissue strips in vitro. This relaxation response is mediated by the increased cAMP synthesis by these agents.     

Roles of prostaglandin on rabbit vesicourethral smooth muscle contraction]

The effects of prostaglandin (PG) E1, E2 and F2 alpha on isolated smooth muscles of rabbit bladder and urethra were studied by in vitro techniques for recording contractile activities. To examine the mechanism of PGs' effect, intracellular cyclic AMP content was also measured by radioimmunoassay. Spontaneous contractile force of muscle strips isolated from rabbit urinary bladder dome and base was increased dose-dependently by administration of PGE1, E2 or F2 alpha. Isolated muscle strips from bladder dome responded to PG more markedly than those from bladder base. The rank order of potency to induce contractile responses was PGF2 alpha greater than PGE2 greater than PGE1 in both dome and base muscles. Spontaneous contractile force of muscle strips isolated from rabbit urethra was increased dose-dependently by administration of PGF2 alpha, and, in contrast, was decreased dose-dependently by PGE1 or E2. These effects were not affected by pretreatment with atropine, phentolamine, propranolol and tetrodotoxin, but were significantly inhibited by pretreatment with verapamil, a Ca-antagonist. Cyclic AMP accumulation in urethral muscle strips significantly increased after administration of PGE1. These results demonstrated that contractile response of rabbit bladder smooth muscle to PG was mainly induced by Ca2+ influx and that cyclic AMP was related to the relaxation of rabbit urethral smooth muscle by PGE1.     

Obstruction alters the effect of prostaglandin E2 on ureteral contractility

BACKGROUND AND PURPOSE: Although our understanding of ureteral physiology during acute obstruction remains limited, we believe that prostanoids (prostaglandins [PGs], thromboxanes, prostacyclins) play a major role in modulation of ureteral contractility and that inhibition of prostanoid synthesis causes substantial reduction in in-vitro and in-vivo ureteral contractility rates. The purpose of this study was to determine the in-vitro effects of PGE2 on chronically obstructed human and acutely obstructed porcine ureters. MATERIALS AND METHODS: Female pigs underwent unilateral laparoscopic ureteral obstruction. Following 1, 2, 6, 24, and 48 hours of obstruction (n = 3 at all points), animals were euthanized, and obstructed, contralateral nonobstructed, and normal (from unobstructed pigs) ureters were harvested. Chronically obstructed human ureter was obtained from subjects who underwent nephrectomy to remove nonfunctioning kidneys. Normal human ureter was obtained from the discarded portion of excess distal ureter in patients undergoing elective donor nephrectomy. Rings 4 to 5 mm long were suspended in aerated Krebs buffer, and their spontaneous contractions and contraction in response to various concentrations of PGE2 were recorded. RESULTS: Prostaglandin E2 increased contractility in chronically obstructed human ureters. In acutely obstructed porcine ureteral segments, low concentrations of PGE2 inhibited ureteral contractility in a dose-dependent fashion, similar to controls. At higher concentrations of PGE2, contractility was increased. This increase was more pronounced with longer intervals of obstruction in a time-dependent manner. CONCLUSION: Prostaglandin E2 increased contractility in obstructed ureters while relaxing normal and nonobstructed ureters. The response to PGE2 was accentuated by a longer duration of obstruction. Prostaglandin E2 may be a unique target for pharmacologic modulation in the treatment of symptoms associated with acute urinary obstruction.     

The effect of prostaglandin E2, 15-methyl prostaglandin E2, and metiamide on established canine gastric mucosal barrier damage.

The ability of two types of gastric acid inhibitor to reverse established gastric mucosal barrier damage was studied in canine Heidenhain pouches. A model of established barrier damage was prepared and validated by perfusing Heidenhain pouches with an acid saline solution containing 20 mmoles of aspirin for 2 hours (damage period) and then perfusing with acid saline alone for a third hour (recovery period). Increases in gastric mucosal permeability to H+ and Na+ produced in the damage period still were present and were significant in the recovery period. In subsequent experiments the effect of topically applied prostaglandin E2 and 15-methyl prostaglandin E2 and intravenously administered prostaglandin E2, 15-methyl prostaglandin E2, and Metiamide on the recovery period permeability was studied. Topical application of the prostaglandins and intravenous Metiamide had no effect on the increased permeability. Intravenously administered prostaglandins returned the permeability to normal and therefore reversed established barrier damage. This effect may have important therapeutic implications in acute gastric mucosal lesions.     

外源性前列腺素E2对兔跟腱胶原含量的影响

目的肌腱损伤后周围前列腺素E2(prostaglandin E2,PGE2)及体外牵伸载荷条件下肌腱细胞产生的PGE2均升高,通过观察外源性PGE2对兔跟腱胶原含量的影响,探讨其与肌腱病发生的关系。方法取健康3～4月龄日本短耳兔24只,体重2.0～2.5 kg,雌雄不限;根据PGE2注射剂量不同随机分为两组(n=12):低剂量组(50 ng)和高剂量组(500 ng)。随机选择一侧后肢跟腱中部经皮注射0.2 mL对应剂量PGE2,对侧对应部位注射0.2 mL生理盐水作为对照,每周注射1次至处死。注射4、8周后两组各处死6只实验动物,大体观察跟腱情况后,取双侧跟腱HE染色观察细胞结构、基质形态,苦味酸-天狼星红染色偏振光显微镜下观察肌腱组织的胶原变化并定量分析Ⅰ、Ⅲ型胶原含量,透射电镜观测胶原纤维密度及直径。结果 HE染色示两组实验侧均出现胶原纤维结构破坏。苦味酸-天狼星红染色示4、8周时两组实验侧Ⅲ型胶原纤维均较对照侧增加,Ⅰ型胶原减少(P<0.05);与低剂量组比较,高剂量组实验侧Ⅲ型胶原纤维增加,Ⅰ型胶原减少,Ⅲ/Ⅰ型胶原比值增高(P<0.05)。透射电镜示两组4、8周时实验侧单位面积内总胶原纤维横截面积所占百分比均较对照侧降低,直径>100 nm的纤维比例均较对照侧降低,直径<100 nm的纤维比例均增加(P<0.05);与低剂量组比较,高剂量组实验侧单位面积内总胶原纤维横截面积所占百分比更低,直径>100 nm的纤维比例均明显降低,直径<100 nm的比例明显增加(P<0.05)。结论重复注射PGE2能导致兔跟腱Ⅰ型胶原减少,Ⅲ型胶原增多,Ⅰ/Ⅲ型胶原比例倒置,单位面积总胶原纤维密度降低,直径变细,可能与肌腱病发生相关。     

The effect of tenoxicam on intraperitoneal adhesions and prostaglandin E2 levels in mice

We determined whether tenoxicam administered intraperitoneally in the preoperative period had an effect on the development of postoperative intraabdominal adhesions (IAA). For this purpose, 100 albino mice were divided into four random groups. Mice in Group 1 were given only 1 mL of 0.9% NaCl intraperitoneally, whereas in Group 2, 1 mL of tenoxicam (150 microg = 5 mg/kg) was administered. After the induction of anesthesia, a median laparotomy was performed, and the bowels were traumatized by touching them with powdered gloves before the incision was closed in Groups 3 and 4. Intraperitoneal tenoxicam was administered to mice in Group 4 after skin closure. All mice were killed after 14 days to determine macroscopic and microscopic IAA; prostaglandin E2 levels were also measured. Postoperative evaluation revealed a reduced IAA formation and a parallel decrease in tissue prostaglandin E2 levels in Group 1 and 2 mice. We conclude that intraperitoneal tenoxicam decreased IAA formation with no peritoneal reaction in the postoperative period. Implications: Postoperative intraabdominal adhesions can cause intestinal obstruction, pelvic pain, or infertility. In this study, we showed that intraperitoneally administered tenoxicam decreases tissue prostaglandin E2 levels and intraabdominal adhesions in mice.     

Age-related changes in contractile force of rabbit detrusor muscle to prostaglandin E1, E2 and F2 alpha

Contractile responses of urinary bladder muscle strips to prostaglandin (PG) E1, E2 and F2 alpha were compared in young and old rabbits. All PGs tested caused an increase in contractile force of urinary bladder muscle strips from young (3 weeks) and old (greater than 2 years) rabbits. The contractile response was most marked with PGE2 at concentrations of 10(-10)-10(-7) M in muscle strips from both young and old rabbits. At a high concentration (10(-5) M), the contractile response was most marked with PGF2 alpha in young rabbit bladder muscle strips, whereas in old rabbit bladder muscle strips the magnitude of the responses to PGE2 and PGF2 alpha were equal at 10(-6) M and both were greater than the response to PGE1. The contractile response to PGE1 was greater in old detrusor than in young detrusor at concentrations greater than or equal to 10(-6) M, whereas the contractile response to PGE2 (10(-7)-10(-5) M) and PGF2 alpha (10(-6)-10(-5) M) were greater in young detrusor than in old detrusor. These data show that rabbit detrusor muscle shows a contractile response to PGE1, E2 and F2 alpha and that the magnitude of these responses vary with age.     

The importance of load-independent analysis in assessment of the inotropic effect of prostaglandin E1 in vivo

Load-independent pressure-dimension analysis was applied in 13 open-chest, anesthetized dogs during either left atrial (n = 7) or right atrial (n = 6) infusion of prostaglandin E1. Right atrial infusion of prostaglandin E1 in doses from 31 to 500 ng/kg/min resulted in no change in any parameters studied, including mean arterial pressure, cardiac output, and systemic and pulmonary vascular resistances. Left atrial infusion of prostaglandin E1 produced dose-dependent reductions in mean arterial pressure and systemic vascular resistance but no change in the slope of the relationship of left ventricular stroke work to end-diastolic length, a load-independent index of ventricular performance. In contrast to findings obtained with load-dependent parameters, these results suggest that prostaglandin E1 has no positive inotropic effect in vivo.     

前列腺素E2受体在前列腺素E2诱导H9c2心肌细胞肥大中的作用

目的 评价前列腺素E2受体(EP受体)在前列腺素E2(PCE2)诱导H9c2心肌细胞肥大中的作用.方法 培养H9c2心肌细胞,以4×104个/ml的密度接种于培养瓶(每瓶3ml)、24孔(每孔1 ml)或6孔(每孔2 ml)培养板.采用随机数字表法,将细胞随机分为4组(n=24):空白对照组(C组)不予任何处理,继续培养48 h;PGE2组在细胞培养液中加入PGE2(终浓度1μmol/L);AH6809组(A组)在细胞培养液中加入PGE2(终浓度1μmol/L)和AH6809(EP1及EP2受体拮抗剂,终浓度10μmol/L);GW627368X组(G组)在细胞培养液中加入PGE2(终浓度1μmol/L)和GW627368X(EP4受体拮抗剂,终浓度10 μmol/L).孵育48 h后采用免疫荧光观察心肌细胞形态,Image J医学图像分析系统测量心肌细胞直径,BCA法检测心肌细胞总蛋白含量,RT-PCR法测定胞浆ANP mRNA及BNP mRNA的表达水平.结果 与C组比较,PGE2组、A组和G组心肌细胞总蛋白含量和心肌细胞直径增加,胞浆ANPmRNA及BNPmRNA表达上调(P＜0.05).与PGE2组比较,G组心肌细胞总蛋白含量和心肌细胞直径降低,胞浆ANP mRNA及BNP mRNA表达下调(P＜0.05),A组上述各指标差异无统计学意义(P＞0.05).结论 EP4受体介导了PGE2诱导的心肌细胞肥大效应,而该效应与EP1和EP2受体无关.     

Increased ex vivo synthesis of prostaglandin E2 by gastric tissue after hemorrhage in rats

Endogenously synthesized prostaglandins are potential mediators of gastrointestinal mucosal protection. Some data suggest that gastric ulceration caused by stressful stimuli is due to diminished mucosal synthesis of prostaglandins. To examine this hypothesis, we determined the effect of hemorrhage, an ulcerogenic stimulus, on ex vivo production of immunoreactive prostaglandin E2 by gastric tissue in the rat. Macroscopic gastric ulcers were reproducibly observed in Sprague-Dawley rats subjected to hemorrhage (3 ml/100 g body weight). The number of ulcers was linearly related to the duration of shock. Prostaglandin E2 synthesis was significantly increased during in vitro incubation of oxyntic and nonoxyntic stomach tissue excised from rats subjected to hemorrhage for 30 minutes (p less than 0.05). These results indicate that damage to the gastric mucosa in rats subjected to hemorrhage occurs despite augmented endogenous secretion of prostaglandin E2. Mechanisms other than impaired prostaglandin biosynthesis were probably responsible for mucosal injury in this model.