Interaction between the LMWH reviparin and aspirin in healthy volunteers

AIMS: To investigate potential interactions between reviparin and acetylsalicylic acid (ASA 300 mg o.d. from day 1-5). METHODS: In an open, randomized, three-way-cross over study nine healthy volunteers received reviparin (s.c. injection of 6300 anti-Xa units) or placebo from days 3 to 5 and acetylsalicylic acid (ASA 300 mg) or placebo from days 1 to 5. Assessments included bleeding time (BT), collagen (1 microg ml-1) induced platelet aggregation (CAG), heptest, plasma antifactor Xa-activity and activated partial thromboplastin time (aPTT). RESULTS: Median bleeding time at day 5 was 5.5 min after reverparin alone and after ASA alone and was 9.6 min after the combination of reviparin and ASA. ASA treatment reduced CAG from 84% to 40 to 50% of Amax; values after combined treatment of reviparin with ASA were not different from those after ASA alone. aPTT was prolonged to 32 s after reviparin; this effect was not modified if subjects received ASA. Combined treatment with ASA and reviparin had no effect on plasma anti-Xa-activity and heptest compared with reviparin alone. CONCLUSIONS: We could not entirely exclude a small interaction between reviparin and ASA on bleeding time, but the effect is probably without clinical significance.     

Actions and interactions of acetylsalicylic acid,salicylic acid and diflunisal on platelet aggregation

Summary Acetylsalicylic acid (ASA) is increasingly employed in the secondary prophylaxis of thromboembolic diseases, due to its capacity to inhibit platelet aggregation. The anti-aggregatory effect of ASA on platelets can be inhibited in vitro by a high concentration of salicylic acid (SA). SA is generated in vivo upon ASA administration, and the SA thus formed might impair the antiplatelet effect of ASA. To assess this possibility, the platelet response to ASA was tested in healthy volunteers before and after medication for 1 week with ASA 1 g t.i.d., with SA 1 g t.i.d., and with the SA derivative diflunisal 0.5 g b.i.d. Pre-medication test doses of 1 g ASA always inhibited platelet aggregation in vivo. Neither treatment with SA nor diflunisal, producing plasma steady-state concentrations of about 1.0 and 0.35 mmol/l, respectively, inhibited platelet aggregation. Nor did administration of SA, diflunisal or ASA itself impair the anti-aggregatory effect of a fresh test dose of ASA. ASA inhibited platelet aggregation in vitro at 0.03 mmol/l, whereas SA and diflunisal failed to impair platelet aggregation until concentrations exceeding 2.0 and 0.5 mmol/l, respectively, were reached. These findings make it unlikely that SA formed upon administration of ASA would impair the anti-aggregating capacity of ASA.     

EFFECTS OF ARGININOSUCCINIC ACID ON NITRIC OXIDE-MEDIATED RELAXATIONS IN RAT AORTA AND ANOCOCCYGEUS MUSCLE

1. Argininosuccinic acid (ASA), a naturally occurring NG derivative of arginine, and the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) were compared for their ability to reduce responses to nitric oxide (NO) derived from endothelial cells (aorta) and nitrergic nerves (anococcygeus muscle). 2. In isolated rings of rat aorta, endothelium-dependent relaxation responses to acetylcholine were abolished by L-NAME (0.1 mmol/L) and were reduced by ASA (0.1 and 0.3 mmol/L). Relaxations induced by sodium nitroprusside (SNP) were not affected by L-NAME but were reduced by ASA. 3. In rat isolated anococcygeus muscles, relaxations elicited by nitrergic nerve stimulation at 1 Hz were abolished by L-NAME (0.1 mmol/L) but were only slightly reduced by ASA (1 mmol/L). The effect of ASA was not sustained. L-Arginine (1 mmol/L) prevented the effect of L-NAME but not that of ASA. Neither ASA or L-NAME inhibited SNP-induced relaxation in the anococcygeus muscle. 4. The results suggest that ASA inhibits NOS but this does not totally account for its effects in reducing NO-mediated relaxations produced by the endothelium-dependent vasodilator acetylcholine in rat aortic rings and stimulation of nitrergic nerves in the rat anococcygeus muscle.     

阿司匹林对TGF-β1诱导的心肌成纤维细胞增殖的抑制作用

目的：研究阿司匹林（ASA）对转化生长因子β1（TGF-β1）诱导心肌成纤维细胞（CFs）异常增殖的干预作用并探讨其可能的作用机制。方法：通过组织块法以及差速贴壁法获得并培养CFs，免疫细胞化学法检测波形蛋白的表达用于鉴定CFs，建立TGF-β1诱导CFs增殖模型，实验分为对照组（无血清DMEM）、TGF-β1组（TGF-β1，20 ng·mL^-1）、TGF-β1+ASA组（ASA，0.5、1、2 μmol·L^-1）。MTT法检测ASA对TGF-β1诱导CFs增殖的影响，羟脯氨酸含量试剂盒检测细胞内以及培养液上清中羟脯氨酸的含量，蛋白质免疫印迹法（Western blot）分析Smad2、Smad3蛋白表达的变化。结果：MTT结果显示，与对照组比较，TGF-β1显著诱导CFs增殖，与TGF-β1组相比，ASA可显著抑制TGF-β1诱导的CFs增殖；羟脯氨酸含量检测显示，与对照组比较，TGF-β1组羟脯氨酸含量明显升高，与TGF-β1组相比，ASA可降低其含量；Western blot结果显示，与对照组比较，TGF-β1显著诱导Smad2、Smad3蛋白水平表达升高，与TGF-β1组相比，ASA可显著降低Smad2、Smad3蛋白水平的表达。结论：ASA对TGF-β1诱导的CFs增殖具有显著的抑制作用，其作用机制可能与抑制TGF-β1/Smads信号通路下游蛋白Smad2、Smad3的表达相关。     

Effects of P2Y(1) receptor antagonism on the reactivity of platelets from patients with stable coronary artery disease using aspirin and clopidogrel

BACKGROUND AND PURPOSE

P2Y₁ is a purine receptor that triggers platelet aggregation. Its inhibition was studied in patients with stable coronary artery disease (CAD) receiving standard anti-platelet therapy.

EXPERIMENTAL APPROACH

Blood samples from 10 patients on aspirin therapy (ASA, 80 mg·day⁻¹) were withdrawn before and 24 h after the administration of 450 mg clopidogrel (ASA/C) and were anti-coagulated with citrate or hirudin/PPACK in the presence or absence of the P2Y₁ inhibitor MRS2179 (M, 100 µM). Platelet responses to ADP (2.5 µM) and TRAP (2.5 µM), and collagen-induced thrombosis under flow conditions were analysed.

KEY RESULTS

Compared with ASA, ASA + M strongly inhibited ADP-induced peak platelet aggregation (88%), late aggregation (84%), P-selectin expression (85%) and α_IIbβ₃ activation (62%) (28%, 65%, 70% and 51% inhibition, respectively, for ASA/C vs. ASA). ASA + M also inhibited platelet/monocyte and platelet/neutrophil conjugate formation by 69% and 71% (57% and 59% for ASA/C vs. ASA). In TRAP-activated blood, ASA + M unexpectedly inhibited α_IIbb₃ activation by 30%. In blood perfused in collagen-coated glass capillaries (shear rate of 1500 s⁻¹), ASA/C prevented thrombus growth beyond 5 min in relation to thrombus fragments embolization. ASA + M with or without clopidogrel completely prevented thrombus formation. Finally, ex vivo addition of MRS2179 and ASA to the blood of healthy donors markedly blocked thrombus formation on collagen in flow conditions, in contrast to ASA plus the P2Y₁₂ inhibitor 2-MeSAMP.

CONCLUSIONS AND IMPLICATIONS

Through particularly efficient complementarities with ASA to inhibit platelet activation and thrombus formation, the inhibition of P2Y₁ in the blood of patients with CAD appears to play a more important role than previously anticipated.     

Interference of NSAIDs with the thrombocyte inhibitory effect of aspirin: A placebo-controlled, ex vivo, serial placebo-controlled serial crossover study

Purpose

Nonsteroidal anti-inflammatory drugs (NSAIDs) and acetylsalicylic acid (ASA) are often prescribed concurrently in patients with nociceptive pain and cardiovascular comorbidity. NSAIDs and ASA inhibit the same COX-enzymes, and thus may interact. ASA’s cardioprotective antiplatelet effect is entirely COX-1 dependent. NSAIDs can be either non-COX-1 and COX-2 selective or COX-2 selective. The aim of this study was to examine the interaction between ASA and different selective and nonselective NSAIDs on thrombocyte function.

Methods

Single-blind, prospective, placebo-controlled, ex vivo, serial crossover trial of 3-day cycles separated by washout periods of at least 12 days in 30 healthy volunteers, evaluating interaction on ASA’s antithrombocyte effect by naproxen, ibuprofen, meloxicam, or etoricoxib taken 2 h before ASA. Ex vivo thrombocyte function, closure time (CT) in seconds, was measured using the Platelet Function Analyzer 100 (PFA-100). CT prolongation during a cycle reflects thrombocyte inhibitory effect. ASA nonresponse was defined as CT prolongation <40 % in the placebo cycle. ASA nonresponders were excluded. Wilcoxon signed-rank was used to evaluate NSAID effect on ASA-induced CT prolongation.

Results

Ibuprofen and naproxen inhibit ASA’s antithrombocyte effect below the nonresponse threshold. Etoricoxib and meloxicam do not cause relevant change in ASA thrombocyte inhibition. Naproxen has an inherent weak thrombocyte inhibitory action below the ASA response threshold.

Conclusions

COX-1 affinity determines the interaction between NSAIDs and ASA on thrombocyte adhesion and aggregation. Ibuprofen and naproxen, but not etoricoxib or meloxicam, taken 2 h before ASA, significantly inhibit ASA’s antithrombocyte effect.     

赖氨匹林对血小板聚集粘附和血栓形成的影响

赖氨匹林（ＬＡＳ）体内给药９０．４ｍｇ·ｋｇ－１（相当于乙酸水杨酸５０ｍｇ·ｋｇ－１）可明显抑制凝血酶和胶原诱导的大鼠血小板聚集，并呈剂量依赖性地抑制ＡＤＰ诱导的血小板聚集。ＬＡＳ９０．４ｍｇ·ｋｇ－１可降低大鼠血小板粘附率，呈剂量依赖性地减轻实验性血栓的重量，同时ＬＡＳ７０ｍｇ·ｋｇ－１可明显延长小鼠尾动脉出血时间。上述结果提示：抑制血小板聚集和降低血小板的粘附性是ＬＡＳ抗血栓和延长小鼠尾动脉出血时间的机制之一。     

Neuroprotective Effects of Acetylsalicylic Acid in Middle Cerebral Artery Occlusion–Induced Brain Ischemia in Rats: Suppression of iNOS,HIF-1α, TNF-α, and Active Caspase-3 Expression

Acetylsalicylic acid (ASA) is neuroprotective through various pharmacological action sites. The aim of this study was to examine the detailed mechanisms underlying the inhibitory effect of ASA in inflammatory and apoptotic responses induced by middle cerebral artery occlusion (MCAO) in rats. In this study, ASA significantly attenuated MCAO-induced focal cerebral ischemia in rats. Administration of ASA at 10–20 mg/kg showed marked reductions in infarct size compared with that of control rats. MCAO-induced focal cerebral ischemia was associated with increases in iNOS, HIF-1α, active caspase-3, and TNF-α mRNA expressions in ischemic regions. These expressions were markedly inhibited by treatment with ASA (20 mg/kg). In conclusion, the neuroprotective effect of ASA may mediate at least a portion of the inhibition of HIF-1α and TNF-α activations, followed by inhibition of apoptosis formation (active caspase-3) and inflammatory response (iNOS), resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, ASA treatment may represent an ideal approach to lowering the risk of or improving function in ischemia-reperfusion brain injury–related disorders.     

Influence of buffered and unbuffered acetylsalicylic acid on dental enamel and dentine in human teeth: an in vitro pilot study.

An in vitro study was conducted to investigate the erosive effect of buffered and unbuffered acetylsalicylic acid (ASA) on dental enamel and dentine in human teeth by scanning electron microscopy. In order to standardize the specimens and to improve comparability the dental enamel and dentine were superficially abraded. The enamel and dentine specimens were therefore particularly sensitive to the influences of acid agents. Concentrated solution of buffered chewable ASA tablets (500 mg ASA and 300 mg calcium carbonate in 5 ml water) showed no changes in the enamel surface structure after exposure times of 1 min, 5 min and 60 min. In contrast, minimal corrosive effects were already seen after exposure of the enamel surface to the unbuffered ASA solutions for 1 min. After exposure times of 5 min and 60 min erosion of the enamel was more pronounced. Immersion in the unbuffered ASA solution led to clearly visible micromorphological changes on the dentine surfaces even after exposure for 1 min. Exposure of the dentine specimens to the buffered ASA solutions led to only very slight changes in the surface morphology. Therefore, the scanning electron micrograph after exposure to buffered ASA is comparable to the picture of untreated dentine.     

Urinary excretion of aspirin.

Six human volunteers were each given single oral doses of aspirin (ASA) ranging from 300-1,500 mg. The unchanged ASA excreted in the urine was proportional to dose and urinary pH. The mean percent (+/- s.d.) of dose excreted was 1.9 +/- 0.67. The clearance for ASA was 1.42 +/- 0.28 1/h. The rate of in vitro hydrolysis of ASA to salicylic acid in urine at 37 degrees C was 4 micrograms/min for an initial ASA concentration of 7.5 mg in 100 ml human urine.     

阿斯匹林、维拉帕米及两药并用对麻醉犬血液动力学的影响

ASA5、10mg·kg~(-1)iv对麻醉犬左室功能和血液动力学指标均无明显影响。Ver0.12mg·kg~(-1)iv可使HR明显减慢,LVWI、TTI、、MAP、TPVR显著降低,FBF明显增加,CI呈增加趋势,LVSP、dP·dt_(max)~(-1).LVEDP等均无明显变化、ASA5mg·kg~(-1)与VerO·12mg·kg~(-1)并用与Ver单用的结果相似,提示ASA不影响Ver改善心血管功能的作用。     

Kinetics and activity of arylsulfatase A in leukocytes derived from patients with cerebral palsy

Activity and kinetics of arylsulfatase A (ASA, EC 3.1.6.8) were analyzed in leukocyte homogenates derived from patients suffering from cerebral palsy. Lower ASA activity was found in the patients' leukocytes than in controls, as determined by spectrophotometry using chromogenic substrate p-nitrocatechol sulfate (p-NCS). Kinetic parameters, K(m) and v(max), for leukocyte ASA were determined from the dependence of initial reaction velocities on the p-NCS concentrations. A slight difference in K(m) values was found for leukocyte enzyme in cerebral palsy (0.26 mmol L(-1)) compared to the control (0.21 mmol L(-1)), whereas v(max) value for leukocyte ASA in disease reached only 58% of the control value. In addition, the presence of the most common mutations associated with ASA pseudo-deficiency (N350S, 1524+95 A>G) and metachromatic leukodystrophy (P426L) was detected in all investigated patients. Changes in activity and kinetic parameters of leukocyte ASA in cerebral palsy are most probably related to the decrease of enzyme concentration; the detected mutations might at least partially contribute to the observed changes.     

Dose loading with delayed-release mesalazine: a study of tissue drug concentrations and standard pharmacokinetic parameters

AIMS: Tissue concentrations of 5-aminosalicylic acid (5ASA) and its metabolites may influence the clinical course of inflammatory bowel disease. Since the factors that determine tissue drug concentrations are unknown we have studied the relationships between the oral dose of delayed-release mesalazine, rectal tissue drug concentrations and standard pharmacokinetic parameters. METHODS: Twelve healthy volunteers were studied following 7 days treatment with 1.2, 2.4 and 4.8 g of delayed-release mesalazine daily. 5-aminosalicylic acid and N-acetyl 5-aminosalicylic acid concentrations were measured in serum, urine, stool and rectal tissue biopsies. RESULTS: Serum concentrations and 24 h urinary excretion of 5ASA and N-acetyl 5ASA increased as the oral dose of mesalazine was increased from 1.2 g through 2.4 g to 4.8 g daily (serum area under curve (AUC):5ASA = 3. 9, 15.4 and 46.8 microg ml-1 h, P < 0.0001; N-acetyl 5ASA = 17.2, 30. 9 and 57.8 microg ml-1 h, P < 0.0001: urinary excretion: 5ASA = 1.8, 85.5 and 445 mg, P < 0.0001; N-acetyl 5ASA = 250, 524 and 1468 mg, P < 0.0001, respectively). Faecal 5ASA excretion increased as the oral dose increased from 1.2 g to 2.4 g but did not increase further with 4.8 g daily dosing whereas faecal N-acetyl 5ASA excretion was similar at all three doses. Rectal tissue concentrations of 5ASA increased markedly, and N-acetyl 5ASA increased modestly, as the dose of oral mesalazine increased from 1.2 g to 2.4 g daily but neither increased further with 4.8 g daily dosing. CONCLUSIONS: The relationship between the ingested dose of delayed-release mesalazine and rectal tissue drug concentrations is complex. Factors other than dose are likely to be important determinants of rectal tissue drug concentrations.     

Influence of cellulose powder structure on moisture-induced degradation of acetylsalicylic acid.

The stability of crystalline acetylsalicylic acid (ASA) powder in binary mixtures with cellulose powders was investigated to reveal information about the influence of the cellulose structural properties on the moisture-induced ASA degradation. Different cellulose powder samples were manufactured and characterized by X-ray diffraction and N2 BET gas adsorption. The degradation patterns in ASA/cellulose mixtures were monitored as a function of salicylic acid increase versus time under various relative humidity conditions at 50 degrees C. The crystallinity index of cellulose samples varied between approximately 49 and 95%. The results indicated that cellulose powder with the lowest crystallinity index exhibited lower degradation rates than the samples with the higher crystallinity index. It should be noted that higher ASA degradation rates were observed in the samples with comparably lower moisture contents. This effect was most pronounced in the 1:3 (w/w), ASA/cellulose mixtures, whereas in 3:1 (w/w), ASA/cellulose mixtures the effect was less obvious. The findings emphasise the importance of cellulose structural organisation when governing the moisture's partition between cellulose and ASA during the hydrolytic degradation.     

Growth inhibition and induction of early apoptosis by arenicolsterol A, a novel cytotoxic enolic sulphated sterol from the marine annelid, Arenicola cristata

Arenicolsterol A (ASA), a novel cytotoxic enolic sulphated sterol, was isolated from the marine annelid, Arenicola cristata (AC). Growth inhibition of this compound on cancer cell lines was determined by MTT assay and suppression of tumour stem cells colony formation. The results showed that ASA was selectively cytotoxic on HeLa cell line (IC(50) = 6.00 +/- 1.16 micromol L(- 1) on HeLa cell line, IC(50) = 10.85 +/- 0.97 micromol L(- 1) on 929 cell line and 14.72 +/- 1.55 micromol L(- 1) on NCI-h6 cell line). In addition, the apoptosis induced by ASA was verified from monitoring the stainability with Annexin V and propidium iodine by a fluorescence-activated cell sorter. The experimental data confirmed that ASA could induce apoptosis in HeLa cells by arresting early stage in apoptosis. Meanwhile, the apoptosis was found to be correlative with the inhibition of the protein tyrosine phosphatases (cdc25A, cdc25B, JSP1, etc). Therefore, ASA might be a novel promising precursor of anticancer medicines.     

Effects of very low dose and enteric-coated acetylsalicylic acid on prostacyclin and thromboxane formation and on bleeding time in healthy subjects

Objective: Low dose acetylsalicylic acid (ASA) is widely used as an anti-aggregatory agent in the primary and secondary prevention of cardiovascular diseases. In an effort to spare prostacyclin formation and to reduce gastrointestinal side-effects, both very low doses and enteric-coated formulations of ASA have been introduced. However, it still remains unclear whether these different formulations and dosages are equally effective with respect to inhibition of platelet aggregation and thromboxane A₂ (TXA₂) formation. Methods: In a randomized study, we therefore investigated the effects of 100?mg ASA plain (p), 100?mg ASA enteric-coated (ec) and 40?mg ASA (p) to 36 healthy male subjects given for 7 days on platelet aggregation and endogenous prostanoid formation rates. Platelet aggregation and platelet TXB₂ release in platelet rich plasma (PRP) and serum TXB₂ and 6-keto-PGF_1α levels were determined at baseline and after 7 days of each medication. The urinary metabolites of TXA₂ (2,3-dinor-TXB₂) and prostacyclin (2,3-dinor-6-keto-PGF_1α) were measured by gas chromatography/tandem mass spectrometry in 24-h-urines at baseline and on day 7 of each medication. Results: Collagen-induced platelet aggregation was 73.1?±?1.6% of maximal aggregation at baseline. It was inhibited by 68.9%, 58.6% and 24.0% by ASA 100?mg plain, 100?mg enteric-coated, and 40?mg plain on day 7, respectively. Platelet TXB₂ release was 11?592.0?± 367.5?pg?·?ml^?1 PRP. It was inhibited by 90.1%, 86.5%, and 55.2% by ASA 100?mg plain, 100?mg enteric-coated, and 40?mg plain, respectively. Serum TXB₂ was almost completely reduced on day?7 by 100?mg ASA, but not by 40?mg ASA; serum 6-keto-PGF_1α was slightly, but significantly reduced in all three groups. Urinary 2,3-dinor-TXB₂ excretion was 196.0?±?41.5?pg?·?mg^?1 creatinine at baseline. It was reduced by 80.3% and 79.1% by ASA 100?mg plain and enteric-coated, respectively (each P?<?0.05 versus baseline), but only by 55.4% by ASA 40?mg plain (P?<?0.05 versus both formulations of ASA 100?mg). Conclusions: Our present data show that the plain and enteric-coated formulations of 100?mg ASA are equally effective in inhibiting platelet aggregation, platelet thromboxane production, and urinary 2,3-dinor-TXB₂ excretion rates. In contrast, a very low dose of 40?mg ASA was significantly less effective in inhibiting these indices of platelet activation in healthy human subjects. ASA enteric-coated 100?mg may be a useful alternative to 100?mg ASA (p) in patients with gastrointestinal side-effects, whereas 40?mg ASA (p) may be too low to inhibit sufficiently platelet activity in patients with cardiovascular diseases in whom platelet activity is increased.     

Adenosine A1 receptors in rat brain synaptosomes: Transductional mechanisms,effects on glutamate release,and preservation after metabolic inhibition

In order to assess a possible synergistic antinociceptive interactions, the analgesic effects of aspirin per s?s (acetyl salicylic acid or “ASA”), a nonsteroidal anti-inflammatory drug (NSAID), and tramadol s.c. (TRA), an atypical opioid analgesic, administered either separately or in combination were determined in a model of pain-induced functional impairment in the rat, groups of six rats received either vehicle, ASA (175.4, 312.1, 555.1, 987.0, 1, 755.3, or 3, 121.2 μmol/kg) and TRA (21.3, 38.0, 67.5, 120.0, or 213.5 μmol/kg), or a combination of ASA and TRA (24 different combinations). This allowed us to detect the interaction profile of these combinations. The ED₅₀ for either ASA or TRA were 1, 173.5 ± 7.4 μmol/kg and 141.5 ± 6.8 μmol/kg, respectively. The data obtained confirmed an interaction between ASA and TRA and showed antinociception that may be additive or synergistic, depending on the drug ratio administered. Furthermore, eight combinations showed various degrees of potentiation (P < .01), whereas the others (16) exhibited analgesic effects not different from that of ASA alone. The combination of ASA (3, 121.2 μmol/kg) and TRA (120.0 μmol/kg) produced the maximum analgesic effect. However, the combination of ASA (987/ μmol/kg) with TRA (120.0 μmo/kg) produced the highest potentiation effects. This study clearly showed (1) that there is an interaction between ASA and TRA and (2) which combination of these analgesic drugs produced either the maximum analgesic effect or the highest degree of potentiation in the rat. © 1995 Wiley-Liss, Inc.     

Activation of genes for spasmolytic peptide, transforming growth factor alpha and for cyclooxygenase (COX)-1 and COX-2 during gastric adaptation to aspirin damage in rats

Background:

NSAIDs, such as aspirin (ASA), cause widespread mucosal damage, but repeated ASA insults appear to induce mucosal tolerance (adaptation) to this?injury. The mechanism of the gastric adaptation to the damage induced by ASA has not been fully explained.

Aim:

To determine the role of the mucosal gene expression for spasmolitic peptide (SP) (a member of trefoil peptides) and transforming growth factor alpha (TGFα) as well as for cyclooxygenase (COX)-1 and COX-2 during gastric adaptation to ASA in rats.

Methods:

Gastric lesions were produced by ASA (100 mg/kg in 1.5 mL of 0.2 M HCl) applied intragastrically (i.g.) as a single dose, every day for 5 days. Control rats were given 1.5 mL of vehicle (0.2 M HCl i.g.) as a single dose, during 5 consecutive days. Gastric blood flow (GBF) was measured by H₂-gas clearance technique and gastric mucosal specimens were taken for the assessment of cell?proliferation rate in gastric mucosa by bromodeoxyuridine (BrdU) uptake, mucosal generation of prostaglandin E₂ measured by radioimmunoassay, and for expression of SP, TGFα COX-1 and COX-2 mRNA as determined by RT-PCR. To quantify the relative amounts of mRNA for SP and TGFα, southern blotting analysis of the PCR products was performed and the intensity of PCR products was compared with that of β-actin used as a standard.

Results:

ASA applied once produced numerous gastric erosions, but with repeated ASA doses the adaptation to this NSAID developed, the area of gastric lesions being reduced by 86% after six consecutive ASA insults. This adaptation to ASA was accompanied by approximately a 90% reduction in prostaglandin E₂ biosynthesis, by a significant rise in BrdU uptake by glandular cells predominantly in the neck region of gastric glands and by expression of SP (SP/β-actin ratio; 0.96 ± 0.08 in ASA-adapted mucosa vs. 0.38 ± 0.05 in the control mucosa) and TGFα (TGFα/β-actin ratio: 0.97 ± 0.07 in ASA-adapted mucosa vs. 0.77 ± 0.06 in the control mucosa). COX-1 expression was detected in vehicle-control gastric mucosa and after single exposure to ASA or after six consecutive ASA insults, while COX-2 mRNA was not detected in vehicle-control gastric mucosa, but appeared after single ASA insult and was sustained after subsequent ASA doses.

Conclusions:

(i) Gastric adaptation to aspirin injury involves enhanced cell proliferation which appears to be mediated by increased expression of SP and TGFα, and (ii) rapid upregulation of COX-2 expression following single and repeated ASA insults may represent a compensatory response to suppression of prostaglandin generation by this NSAID.