Evaluation of bronchial challenge test results for use in assessment of paediatric eczema: a retrospective series.

BACKGROUND: Atopic dermatitis (AD), asthma, and allergic rhinitis are associated diseases involved in the atopic march. The bronchial challenge test (BCT) is a tool that evaluates airway hyperresponsiveness in patients with asthma. This study aimed to evaluate whether a positive BCT result is useful in assessment of paediatric AD. METHODS: This retrospective case series included 284 patients with AD who had BCT results. Clinical information and laboratory parameters were reviewed, including AD severity (using the SCORing Atopic Dermatitis [SCORAD]), skin hydration, and transepidermal water loss. RESULTS: Of the 284 patients who had BCT, 106 had positive BCT results and 178 had negative BCT results. A positive BCT result was associated with a history of asthma (P<0.0005), sibling with asthma (P=0.048), serum immunoglobulin E (P=0.045), eosinophil count (P=0.017), and sensitisation to food allergens in the skin prick test (P=0.027). There was no association between a positive BCT result and personal allergic rhinitis, parental atopy, sibling allergic rhinitis or AD, skin prick response to dust mites, objective SCORAD score, skin hydration, transepidermal water loss, exposure to smoking, incense burning, cat or dog ownership, or AD treatment aspects (eg, food avoidance and traditional Chinese medicine). Logistic regression showed significant associations of a positive BCT result with a history of asthma (adjusted odds ratio=4.05; 95% confidence interval=1.92-8.55; P<0.0005) and sibling atopy (adjusted odds ratio=2.25; 95% confidence interval=1.03-4.92; P=0.042). CONCLUSIONS: In patients with paediatric AD, a positive BCT result was independently and positively associated with personal history of asthma and sibling history of atopy, but not with any other clinical parameters.

Measures of socioeconomic status and self-reported glaucoma in the U.K. Biobank cohort.

PURPOSE: To determine ocular, demographic, and socioeconomic associations with self-reported glaucoma in the U.K. Biobank. METHODS: Biobank is a study of U.K. residents aged 40-69 years registered with the National Health Service. Data were collected on visual acuity, intraocular pressure (IOP), corneal biomechanics, and questionnaire from 112,690 participants. Relationships between ocular, demographic, and socioeconomic variables with reported diagnosis of glaucoma were examined. RESULTS: In all, 1916 (1.7%) people in U.K. Biobank reported glaucoma diagnosis. Participants reporting glaucoma were more likely to be older (mean 61.4 vs. 56.7 years, P<0.001) and male (2.1% vs. 1.4%, P=0.001). The rate of reported glaucoma was significantly higher in Black (3.28%, P<0.001) and Asian (2.14%, P=0.009) participants compared with White participants (1.62%, reference). Cases of reported glaucoma had a higher mean IOP (18 mm Hg both eyes, P<0.001), lower corneal hysteresis (9.96 right eye, 9.89 left eye, P<0.001), and lower visual acuity (0.09 logMAR right eye, 0.08 logMAR left eye, P<0.001) compared with those without (16 mm Hg both eyes, hysteresis 10.67 right eye, 10.63 left eye, 0.03 logMAR right eye, 0.02 logMAR left eye). The mean Townsend deprivation index was -0.72 for those reporting glaucoma and -0.95 for those without (P<0.001), indicating greater relative deprivation in those reporting glaucoma. Multivariable logistic regression showed that people in the lowest income group (<£18,000/year) were significantly more likely to report a diagnosis of glaucoma compared with any other income level (P<0.01). We observed increasing glaucoma risk across the full range of income categories, with highest risk among those of lowest income, and no evidence of a threshold effect. CONCLUSIONS: In a large U.K. cohort, individuals reporting glaucoma had more adverse socioeconomic characteristics. Study of the mechanisms explaining these effects may aid our understanding of health inequality and will help inform public health interventions.

Antiplatelet effect of marchantinquinone, isolated from Reboulia hemisphaerica, in rabbit washed platelets.

Platelet activation is involved in serious pathological situations, including atherosclerosis and restenosis. It is important to find efficient antiplatelet medicines to prevent fatal thrombous formation during the course of these diseases. Marchantinquinone, a natural compound isolated from Reboulia hemisphaerica, inhibited platelet aggregation and ATP release stimulated by thrombin (0.1 units mL(-1)), platelet-activating factor (PAF; 2 ng mL(-1)), collagen (10 microg mL(-1)), arachidonic acid (100 microM), or U46619 (1 microM) in rabbit washed platelets. The IC50 values of marchantinquinone on the inhibition of platelet aggregation induced by these five agonists were 62.0 +/- 9.0, 86.0 +/- 7.8, 13.6 +/- 4.7, 20.9 +/- 3.1 and 13.4 +/- 5.3 microM, respectively. Marchantinquinone inhibited thromboxane B2 (TxB2) formation induced by thrombin, PAF or collagen. However, marchantinquinone did not inhibit TxB2 formation induced by arachidonic acid, indicating that marchantinquinone did not affect the activity of cyclooxygenase and thromboxane synthase. Marchantinquinone did inhibit the rising intracellular Ca2+ concentration stimulated by the five platelet-aggregation inducers. The formation of inositol monophosphate induced by thrombin was inhibited by marchantinquinone. Platelet cAMP and cGMP levels were unchanged by marchantinquinone. The results indicate that marchantinquinone exerts antiplatelet effects by inhibiting phosphoinositide turnover.

Aggregation inhibitory activity of minor acetophenones from Paeonia species.

Two minor acetophenones, 2,5-dihydroxy-4-methoxy-acetophenone (2) and 2,5-dihydroxy-4-methylacetophenone (7) from Paeonia species were found to selectively inhibit the aggregation of rabbit platelets induced by arachidonic acid. They were more potent than the major compound, paeonol (1), and 7 also inhibited the formation of TXA2 and PGD2 from arachidonic acid.

Evaluation of the efficacy of a hospital-based asthma education programme in patients of low socioeconomic status in Hong Kong.

BACKGROUND: Good asthma control requires optimal medical treatment in conjunction with appropriate self-management. In the West, the effectiveness of patient education on improving self-management has been well documented. However, data amongst Asian populations are lacking. We performed a pilot study to evaluate the efficacy of a hospital based education programme aimed at improving self-management skills and reducing morbidity in a Chinese population with low socioeconomic status and education level. METHODS: Our asthma education programme was a low-cost programme conducted in essence by specialist respiratory nurses. Patients attending our asthma clinic were instructed during a two-hour educational session on the pathophysiology of asthma, its potential triggers, the appropriate use of medications including proper inhaler techniques, and the self-management of their disease. These instructions were reinforced by video sessions at subsequent outpatient clinic attendance when patients' inhaler and peak flow techniques were checked by the same nurses and their self-management plan re-examined by the attending physicians. Asthma knowledge, inhaler technique, FEV1 and peak expiratory flow (PEF), and patients' self-rating of their asthma were determined at baseline, 6 months and 1 year after the intervention. Morbidity was assessed by the numbers of hospitalizations, unscheduled visits to family physicians and accident and emergency department attendance, courses of oral steroid used and days off work or school at baseline and 1 year. RESULTS: Two hundred and thirty patients were recruited for the study, 83% completing the entire assessment period. The group demonstrated significant improvements in lung function: the mean FEV1 +/- SD increased from 63.6 +/- 20.6% of predicted values at baseline to 68.5 +/- 22.3% at 6 months and 68.6 +/- 22.8% at 1 year (P < 0.05), and the mean PEF +/- SD increased from 64.6 +/- 23.0% of predicted values at baseline to 75.4 +/- 27.0% at 6 months and 76.8 +/- 24.5% at 1 year(P < 0.001). There were also significant improvements in inhaler technique (P < 0.01), asthma knowledge (P < 0.001), patients' self-rating of their asthma (P < 0.05), and reductions in the numbers of hospitalizations (P < 0.01), visits to family physicians (P < 0.001) and accident and emergency department attendance (P < 0.001) during the study period. Patients with moderate to severe asthma as defined by an FEV1 of < 80% of predicted values were most likely to benefit from the programme. CONCLUSIONS: We conclude that patient education is likely to be an essential component in the holistic approach to the management of asthma even amongst Asian populations of low socioeconomic status and education level. Further studies using randomised controlled trials are necessary to consolidate our findings.

Antiplatelet action of 3',4'-diisovalerylkhellactone diester purified from Peucedanum japonicum Thunb.

3',4'-Diisovalerylkhellactone diester (PJ-1) is a coumarin derivative purified from the medicinal herb Peucedanum japonicum Thunb. We examined its in vitro effects on various aspects of platelet reactivity. PJ-1 inhibited the aggregation and ATP release of rabbit platelets induced by PAF (platelet-activating factor) and collagen. The IC50 values of PJ-1 and BN52021 on PAF (2 ng/ml)-induced platelet aggregation were about 56.3 and 22.0 microM, respectively. And, the IC50 value of PJ-1 toward collagen (10 microg/ml)-induced platelet aggregation was 89.4 microM. Although the platelet aggregation caused by arachidonic acid and thrombin were barely inhibited by PJ-1, the release reactions were partially suppressed. PJ-1 also inhibited the thromboxane B2 formation caused by collagen, while formations of thromboxane B2 and prostaglandin D2 caused by arachidonic acid were not affected. The phosphoinositide breakdown caused by PAF was inhibited by PJ-1, but those by other inducers were not affected significantly. PJ-1 inhibited the intracellular Ca2+ increase caused by PAF in fura-2-loaded platelets. PJ-1 also concentration-dependently inhibited [3H]PAF (3.03 ng/ml) binding to washed platelets with an IC50 value of 3.9 microM. It is concluded that the main antiplatelet effect of PJ-1 may be due to dual activities on the blockade of PAF receptor-induced activation and also the inhibition of phospholipase A2 in rabbit platelets.

Scavenger and antioxidant properties of prenylflavones isolated from Artocarpus heterophyllus.

The antioxidant properties of prenylflavones, isolated from Artocarpus heterophyllus Lam., was evaluated in this study. Among them, artocarpine, artocarpetin, artocarpetin A, and cycloheterophyllin diacetate and peracetate had no effect on iron-induced lipid peroxidation in rat brain homogenate. They also did not scavenge the stable free radical 1,1-diphenyl-2-picrylhydrazyl. In contrast, cycloheterophyllin and artonins A and B inhibited iron-induced lipid peroxidation in rat brain homogenate and scavenged 1,1-diphenyl-2-picrylhydrazyl. They also scavenged peroxyl radicals and hydroxyl radicals that were generated by 2,2'-azobis(2-amidinopropane) dihydrochloride and the Fe3+-ascorbate-EDTA-H2O2 system, respectively. However, they did not inhibit xanthine oxidase activity or scavenge superoxide anion, hydrogen peroxide, carbon radical, or peroxyl radicals derived from 2,2'-azobis(2,4-dimethylvaleronitrile) in hexane. Moreover, cycloheterophyllin and artonins A and B inhibited copper-catalyzed oxidation of human low-density lipoprotein, as measured by fluorescence intensity, thiobarbituric acid-reactive substance and conjugated-diene formations and electrophoretic mobility. It is concluded that cycloheterophyllin and artonins A and B serve as powerful antioxidants against lipid peroxidation when biomembranes are exposed to oxygen radicals.

Antiplatelet agents isolated from medicinal plants.

Platelet-vessel wall interaction is an important process in physiological hemostasis and pathological thrombosis. In oriental countries, some medicinal plants have been claimed for uses to improve circulation, induce fibrinolysis or prevent thrombosis. In cooperation with chemists using bioassay-based step-by-step purification, some antiplatelet agents were isolated from plant sources. According to their effects on platelet aggregation, release reaction and signal transductions involved, these antiplatelet agents can be classified into eight groups: 1. platelet-activating factor (PAF) antagonists, 2. collagen-receptor antagonists, 3. thromboxane-receptor antagonists, 4. ADP-receptor agonists, 5. inhibitors of phosphoinositide breakdown, 6. inhibitors of thromboxane formation, 7. agents increasing cyclic nucleotides, and 8. protein kinase C activators. These new pharmacological agents derived from medicinal plant sources may be useful as leads to develop as effective cardiovascular drugs.

Bioactive constituents of Morus australis and Broussonetia papyrifera.

The biological activities of the active principles of two plants in the Moraceae have been investigated. A new prenylflavonoid, australone A (1), and a new triterpenoid, 3 beta-[(m-methoxybenzoyl)oxy]urs-12-en-28-ioc acid (2) were isolated from the root bark of Morus australis, and their structures determined by spectroscopic methods. Also isolated from this plant were seven known compounds, morusin (3), kuwanon C (4), betulinic acid, beta-amyrin, quercetin, ursolic acid, and compound A. Morusin (3) showed significant effects on arachidonic acid-, collagen-, and PAF-induced platelet aggregation, while kuwanon C (4) was active in the arachidonic acid- and PAF-induced platelet aggregation assays. In biological work on a second plant, Broussonetia papyrifera, broussoflavonols F (5) and G (6), broussoflavan A (7), and broussoaurone A (8) potently inhibited Fe(2+)-induced lipid oxidation in rat-brain homogenate. Compounds 5-7 also significantly inhibited the proliferation of rat vascular smooth muscle cells.

Bioactive alkaloids from Illigera luzonensis.

Using antiplatelet aggregation as a guide to fractionation, seven aporphines, actinodaphnine (1), N-methylactinodaphnine (2), launobine (3), dicentrine (4), O-methylbulbocapnine (5), hernovine (7), and bulbocapnine (9), and two oxoaporphines, dicentrinone (6) and liriodenine (8), were isolated from the stems of Illigera luzonensis. Among them, compounds 2, 4, 5, 8, and 9 were isolated for the first time from this species. Moreover, compounds 1-5, and 8 showed significant antiplatelet aggregation and compounds 1 and 6 exhibited significant vasorelaxant activities, respectively.

ADP-mimicking platelet aggregation caused by rugosin E, an ellagitannin isolated from Rosa rugosa Thunb.

Among the nine ellagitannins, rugosin E was the most potent platelet aggregating agent with an EC50 of 1.5 +/- 0.1 microM in rabbit platelets and 3.2 +/- 0.1 microM in human platelets. The aggregations caused by rugosin E and ADP were inhibited by EGTA, PGE1, mepacrine, sodium nitroprusside and neomycin, but not by indomethacin, verapamil, TMB-8, BN52021 and GR32191B. Rugosin E-induced thromboxane formation was suppressed by indomethacin, EGTA, PGE1, verapamil, mepacrine, TMB-8 and neomycin. ADP-scavenging agents, such as CP/CPK and apyrase inhibited concentration-dependently ADP (20 microM)-, but not rugosin E (5 microM)-induced platelet aggregation. In thrombin (0.1 U/ml)-treated and degranulated platelets, rugosin E and ADP still caused 63.5 +/- 3.0% and 61.2 +/- 3.5% of platelet aggregation, respectively. Selective ADP receptor antagonists, ATP and FSBA inhibited rugosin E- and ADP-induced platelet aggregations in a concentration-dependent manner. Both rugosin E and ADP did not induce platelet aggregation in ADP (1 mM)-desensitized platelets. In contrast to ADP, rugosin E did not decrease cAMP formation in washed rabbit platelets. Both rugosin E and ADP did not cause phosphoinositide breakdown in [3H]myo-inositol-labeled rabbit platelets. In fura-2/AM-load platelets, both rugosin E and ADP induced increase in intracellular calcium concentration and these responses were inhibited by ATP and PGE1. All these data suggest that rugosin E may be an ADP receptor agonist in rabbit platelets.

Pharmacological evaluation of ocoteine, isolated from Cassytha filiformis, as an alpha 1-adrenoceptor antagonist in rat thoracic aorta.

Ocoteine, isolated from Cassytha filiformis, was found to be an alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of phenylephrine-induced vasoconstriction (pA2 = 7.67 +/- 0.09). Removal of endothelium from the aorta did not affect its antagonistic potency (pA2 = 7.97 +/- 0.07). [3H]-Inositol monophosphate formation caused by noradrenaline (3 microM) was suppressed by ocoteine (10 microM) and prazosin (3 microM). Ocoteine did not affect the contraction induced by U-46619, prostaglandin F2 alpha or angiotensin II, but inhibited slightly those by high K+ and endothelin I. Neither the cyclic AMP nor cyclic GMP content of rat thoracic aorta was changed by ocoteine (10 microM). Comparing the EC50 values, the potency of ocoteine against 5-hydroxytryptamine (5-HT) was about 60 times less than that against phenylephrine. Ocoteine (10 microM) also slightly antagonized the clonidine-induced inhibition of the twitch response evoked by field stimulation in rat vas deferens. In guinea pig trachea, the contraction caused by carbachol, histamine, neurokinin A or leukotriene C4 and beta 2-adrenoceptor-mediated relaxing responses induced by isoprenaline were not affected by ocoteine (10 microM). The voltage clamp study in rat ventricular single myocytes revealed that ocoteine (3, 10 microM) inhibited steady state outward currents, but not transient outward currents or slow inward Ca2+ currents. It is concluded that ocoteine is a selective alpha 1-adrenoceptor antagonist in isolated rat thoracic aorta. At high concentrations, it also blocks 5-HT receptors and Na+ and steady state outward currents in rat ventricular myocytes.

Antiplatelet arylnaphthalide lignans from Justicia procumbens.

Fractionation of the EtOH extract of Justicia procumbens, guided by antiplatelet bioassay, led to the isolation of nine known arylnaphthalide lignans, neojusticin A (1), justicidin B (2), justicidin A (3), taiwanin E methyl ether (4), neojusticin B (5), chinensinaphthol methyl ether (6), taiwanin E (8), chinensinaphthol (9), and diphyllin (10), and a new arylnaphthalide lignan that was characterized by spectral means as 4'-demethylchinensinaphthol methyl ether (7). Compounds 1, 2, 4, and 8 significantly inhibited platelet aggregation.

Novel antiplatelet constituents from formosan moraceous plants.

Sixteen constituents from Formosan Moraceous plants were tested for their antiplatelet activities in rabbit platelet suspension and human platelet-rich plasma. Cycloartocarpin A, cycloheterophyllin, broussochalcone A, kazinol A, broussoaurone A, and broussoflavonol F showed strong inhibition of arachidonic acid (AA)-induced platelet aggregation. Of the compounds tested, broussochalcone A exhibited the most potent inhibition of platelet aggregation induced by AA (IC50 = 6.8 microM). The antiplatelet effects of cycloheterophyllin, broussochalcone A, kazinol B, broussoaurone A, and broussoflavonol F are partially due to an inhibitory effect on cyclooxygenase.

Beneficial effect of Aloe on wound healing in an excisional wound model.

Recent evidence from in vitro and in vivo experiments suggests that topical antimicrobials may be toxic to fibroblasts and keratinocytes and retard wound healing. The purpose of this study was to determine the effects of Aloe, a potential wound-healing agent, on wound contraction in excisional wounds treated with topical antimicrobials. Sprague-Dawley rats were prepared with four 1.5 cm2 dorsal defects through the skin and panniculus. The animals were divided into five groups (n = 10 per group): (1) Aloe, (2) NaOCl solution (0.025%), (3) mafenide acetate, (4) mafenide acetate + Aloe, and (5) control. Wounds were treated topically for 14 days 3 times a day. Serial standard photographs and serial wound planimetry were performed weekly. Following healing, the breaking strength of each resultant scar was determined using an Instron tensiometer. Kruskal-Wallis, ANOVA, and multiple comparison methods were used for data analysis. Aloe and NaOCl solution significantly accelerated wound contraction (p < 0.05). In the mafenide acetate + Aloe group, contraction was similar to the control, whereas the mafenide acetate alone retarded wound healing. The addition of Aloe in combination and alone in wounds increased the breaking energy when compared to controls (p < 0.05). Aloe appears to expedite wound contraction and neutralize the wound retardant effect seen with the topical mafenide acetate alone. This effect appears to be due to an increased collagen activity, which is enhanced by a lectin, consequently improving the collagen matrix and enhancing the breaking strength.

Antiplatelet and vasorelaxing actions of some aporphinoids.

A series of aporphines and oxoaporphines was tested for antiplatelet and vasorelaxing actions. (+)-N-Methylactinodaphnine, (-)-norannuradhapurine x HBr, xylopine, actinodaphnine, and N-methylnandigerine showed strong inhibition of adenosine 5'-diphosphate (ADP)-induced platelet aggregation. Boldine, (+)-N-methylactinodaphnine, (-)-norannuradhapurine x HBr, xylopine, N-acetyllaurolitsine, N-methyllaurotetanine, actinodaphnine, N-methylnandigerine, O-methylbulbocapnine, and liriodenine showed strong inhibition of arachidonic acid (AA)-induced platelet aggregation. (+)-N-Methylactinodaphnine, fissoldine x HCIO4, (-)-norannuradhapurine x HBr, xlylopine, N-methyllaurotetanine, actinodaphnine, N-methylnandigerine, O-methylbulbocapnine, and liriodenine showed strong inhibiton of collagen-induced platelet aggregation. (-)-Norannuradhapurine x HBr, xylopine, N-methyllaurotetanine, and actinodaphnine showed strong inhibition of platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine)-induced platelet aggregation. (+)-N-Methylactinodaphnine, laurotetanine, N-methylactinodaphnine N-oxide, oxoglaucine, boldine, and actinodaphnine showed vasorelaxing action in rat thoracic aorta. The results are discussed on the basis of structure-activity relationships.

Indolopyridoquinazoline alkaloids with antiplatelet aggregation activity from Zanthoxylum integrifoliolum.

Bioassay-guided fractionation led to the isolation of three indolopyridoquinazoline alkaloids, 1-hydroxyrutaecarpine, rutaecarpine, and 1-methoxyrutaecarpine as the active principles of antiplatelet aggregation in vitro, from the chloroform-soluble part of the fruit of Zanthoxylum integrifoliolum (Rutaceae). 1-Hydroxyrutaecarpine exhibited antiplatelet activity induced by AA and showed an IC50 value of ca. 1-2 micrograms/ml.

Coumarins and antiplatelet aggregation constituents from Formosan Peucedanum japonicum.

Four new khellactone esters, (-)-trans-3'-acetyl-4'-senecioylkhellactone, (+-)-cis-3'-acetyl-4'-tigloylkhellactone, (+-)-cis-4-tigloylkhellactone, (+)-trans-4'-tigloylkhellactone, together with 14 known coumarins, isoimperatorin, psoralen, bergapten, xanthotoxol, cnidilin, (-)-selinidin, (-)-deltoin, (+)-pteryxin, (+)-peucedanocoumarin III, xanthotoxin, imperatorin, (+)-marmesin, (+)-oxypeucedanin hydrate, (+)-peucedanol and three chromones, eugenin, (-)-hamaudol, (+)-visamminol, have been isolated from the root of Formosan Peucedanum japonicum. The structures of the new compounds were elucidated by spectral data. The identities of (+)-trans-3'-tigloyl-4'-acetylkhellactone, formerly reported as a new compound, and (+)-cis-3'-angeloyl-4'-acetyl-khellactone, with the known (+)-peucedanocoumarin III and (+)-pteryxin, respectively, are discussed. Among the isolates, seven compounds, eugenin, (-)-selinidin, (+)-pteryxin, imperatorin, bergapten, cnidilin and (+)-visamminol, show strong antiplatelet aggregation activity in vitro.

Novel antiplatelet naphthalene from Rhamnus nakaharai.

A new naphthalene derivative, isotorachrysone [1], was isolated from the stem bark of Rhamnus nakaharai along with several known compounds. The antiplatelet effects of isotorachrysone [1], isotorachrysone peracetate [2], 6-methoxysorigenin [3], quercetin 3-O-methyl ether [4], and quercetin 3-O-methyl ether peracetate [5] were studied using washed rabbit platelets. Of the compounds tested, 1, 2, 4, and 5 showed potent antiplatelet effects on arachidonic acid (AA-) and collagen-induced platelet aggregation. Compound 5 also showed potent antiplatelet effects on platelet-activating factor-(PAF-) induced platelet aggregation. Isotorachrysone [1] and its peracetate [2] were also studied for antiplatelet activity in human platelet-rich plasma (PRP) and both showed potent inhibition of the secondary aggregation induced by epinephrine. The antiplatelet effects of 1 and 2 are due partially to an inhibitory effect on thromboxane formation.

Inhibition on platelet activation by shikonin derivatives isolated from Arnebia euchroma.

Acetylshikonin, teracrylshikonin, beta,beta-dimethylacrylshikonin and shikonin, isolated from Arnebia euchroma, inhibited collagen (10 micrograms/ml)-induced aggregation of washed rabbit platelets in a concentration-dependent manner with IC50 values of 2.1 +/- 0.2, 2.8 +/- 0.3, 4.2 +/- 0.5 and 10.7 +/- 0.7 microM, respectively. Acetylshikonin also inhibited the aggregation and ATP release of washed rabbit platelets induced by arachidonic acid (AA, 100 microM), U46619 (1 microM), platelet-activating factor (PAF, 3.6 nM) and thrombin (0.1 U/ml) in a concentration-dependent manner. The IC50 values of acetylshikonin on the inhibition of these four agonists-induced platelet aggregation were 3.1 +/- 0.4, 2.2 +/- 0.2, 8.0 +/- 0.6 and 12.7 +/- 1.0 microM, respectively. The thromboxane B2 formation caused by collagen, PAF and thrombin was inhibited by acetylshikonin, while formations of thromboxane B2 and prostaglandin D2 caused by AA were not inhibited. Acetylshikonin did not inhibit cyclooxygenase activity since it did not attenuate prostaglandin E2 formation after incubation of sheep vesicular gland microsomes with AA. Acetylshikonin suppressed both the rise of intracellular Ca2+ concentration and the generation of [3H]inositol monophosphate caused by these five aggregation inducers. Platelet cyclic AMP level was unaffected by acetylshikonin. These data indicate that acetylshikonin inhibits platelet activation by suppression of phosphoinositide breakdown.