Inhibitory effect of KW-4679, an anti-allergic drug, on tachykinin-mediated airway response induced by electrical vagal stimulation in guinea pigs

We examined the effect of KW-4679 ((Z)-11-[(3-dimethylamino) propylidene]-6,11-dihydro-dibenz[b,e]oxepin-2-acetic acid monohydrochloride), an anti-allergic drug, on the tachykinin-mediated airway response in guinea pigs. Electrical stimulation of the vagus nerve in atropine-treated and propranolol-treated guinea pigs caused a 38.1% decrease in dynamic compliance (Cdyn), which was suppressed by the combination of the tachykinin NK1-receptor antagonist (+/-)-CP-96345 and NK2-receptor antagonist SR 48968. KW-4679 at a dose of 3 mg/kg significantly reduced the decrease in Cdyn (P < 0.05). On the other hand, KW-4679 did not inhibit substance P or neurokinin A-induced decrease in Cdyn. These results suggest that KW-4679 may inhibit the tachykininergic airway response by prejunctional inhibition of peripheral sensory nerves.

Gene expression of the human prostaglandin E receptor EP4 subtype: differential regulation in monocytoid and lymphoid lineage cells by phorbol ester

We isolated a cDNA clone encoding the human prostaglandin (PG) E receptor EP4 subtype and examined the gene expression in human blood cells. Northern blot analysis revealed that the EP4 gene is expressed at a high level in peripheral blood mononuclear cells, and at lower levels in cultured human blood cell lines, THP-1 and U937 (monocytoid cell lines), MOLT-4 and Jurkat (T-cell lines), and Raji (B-cell line). To examine regulation of the EP4 gene expression in the immune system, we studied the effects of phorbol 12-myristate 13-acetate (PMA) on these cell lines. Gene expression was upregulated in THP-1, U937, and Raji cells by PMA, and was downregulated in MOLT-4 and Jurkat cells. In THP-1 cells the effects of PMA were further analyzed, and the upregulation of the EP4 gene was shown to be followed by an increase in PGE2 binding sites and in PGE2-induced cAMP accumulation. In the striking contrast, other PGE receptor subtypes (EP1, EP2 and EP3) and other prostanoid receptors (IP and DP) were shown not to be upregulated by PMA. Therefore, this is the first demonstration of a highly specific upregulation of the EP4 subtype in THP-1 cells treated with PMA, suggesting the importance of the EP4 subtype in the immune system. In the present study we also clarified that EP4 gene expression is regulated differently among human monocytoid and lymphoid lineage cells, thus leading to the better understanding of the regulatory mechanisms for the human EP4 gene expression in the immune system.

Prevention of hydrogen peroxide damage by soybean saponins to mouse fibroblasts

Soybean saponin is one of several soybean glycosides. Recently, new soybean saponins which possess the DDMP (2,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one) moiety have been detected. Soyasaponin beta g of these new soybean saponins was shown to inhibit hydrogen peroxide damage to mouse fibroblast cells. Not only the new saponin but also soyasaponin I, which has lost the DDMP moiety from soyasaponin beta g, was tested and showed higher inhibition in this assay. In order to investigate the relationship between the effect and chemical structure, glycyrrhizin, which has a similar chemical structure to soyasaponin I, was also tested and exhibited the same effect as soyasaponins beta g and I. Soyasaponin Ab, a major authentic bisdesmosidic saponin that exists only in the soybean hypocotyl, was also tested and exhibited the highest inhibition of hydrogen peroxide damage among the four saponins. It was concluded that water-soluble soybean saponins protected the cells from damage by hydrogen peroxide.

Mechanisms of the suppression of the bladder activity by flavoxate

BACKGROUND

This study was designed to clarify the primary site of action of flavoxate, clinically used for the treatment of urinary frequency.

METHODS

In rats, the effect of flavoxate on contractile responses in isolated detrusor strips, bladder contraction induced by pelvic nerve stimulation, isovolumetric rhythmic bladder contractions, and pelvic nerve activity were examined. In decerebrated cats, flavoxate was microinjected into the nuclei in the pons, and its effect on reflex micturition was observed.

RESULTS

Flavoxate suppressed carbachol- and calcium ion (Ca2+)-induced contractions of isolated detrusor strips in a noncompetitive and a competitive manner, respectively. Intravenous flavoxate suppressed both initial phasic, and later tonic, bladder contractions induced by electrical stimulation of the distal end of the pelvic nerve. It abolished isovolumetric rhythmic bladder contractions and the associated efferent pelvic nerve activity, without affecting baseline vesical pressure and afferent pelvic nerve activity. When administered intracerebroventricularly or intrathecally, it abolished isovolumetric rhythmic bladder contractions. Flavoxate microinjected into the nucleus reticularis pontis oralis (PoO; pontine micturition inhibitory region) of decerebrated cats inhibited the reflex micturition, but had no effect when microinjected into the locus coeruleus alpha (pontine micturition center) or locus subcoeruleus (pontine urine storage center).

CONCLUSIONS

Flavoxate suppressed the micturition reflex primarily by facilitating the inhibitory action of the PoO on the descending pathways from the pontine micturition center to the sacral parasympathetic intermediolateral nuclei.

KW-4679, an antiallergic drug, inhibits the production of inflammatory lipids in human polymorphonuclear leukocytes and guinea pig eosinophils

The effects of (Z)-11-[(3-dimethylamino)propylidene]-6,11-dihydrodibenz [b.e.]oxepin-2-acetic acid monohydrochloride (KW-4679), an orally active antiallergic drug, on the production of platelet-activating factor (PAF), leukotriene (LT) and thromboxane (TX) induced by Ca2+ ionophore A23187 were examined. KW-4679 at 10 microM reduced the amount of cell-associated PAF by 52.8% in human polymorphonuclear leukocytes (PMNs). KW-4679 (1-100 microM) also inhibited the release of both LTB4 and TXB2, a stable metabolite of TXA2, by human PMNs in a concentration-dependent manner, but did not influence the release of beta-glucuronidase. The 50% inhibitory concentration (IC50) values for LTB4 and TXB2 release were 5.9 and 6.0 microM, respectively. In guinea pig eosinophils, KW-4679 inhibited the release of peptide LTs at a concentration higher than 10 microM (IC50 = 66.9 microM). KW-4679 failed to inhibit PAF acetyltransferase, 5-lipoxygenase and TX synthase, but inhibited the arachidonic acid release by human PMNs in a concentration-dependent manner in a similar concentration as that inhibiting production or release of lipid mediators (IC50 = 19.5 microM). These results indicate that KW-4679 suppresses LTs and TX release and PAF formation by reducing arachidonic acid release from phospholipids, probably through interference with phospholipase A2. The inhibitory action of KW-4679 on PAF, LT and TX production is a beneficial effect of an antiallergic drug.

[A case of posterior tuberculous spondylitis of the lumbar vertebra with the skull inoculated by acupuncture]

A 77-year-old male consulted an orthopedist with complaints of lumbago and a lumbar swelling, and was treated with acupuncture. As the symptoms deteriorated, and smear of a specimen aspirated from the lumbar swelling was positive for acid fast bacilli which were later identified as Mycobacterium tuberculosis, he was hospitalized in the National Chiba Higashi Hospital. On admission to our hospital, CT-scan of lumbar vertebrae showed the destructive change of spinous process of the third lumbar vertebra accompanied by the abscess formation, and an occipital swelling with the destructive change of skull was also detected. Whole body examinations with CT-scan and bronchoscopy did not reveal any other abnormal findings suspective of tuberculous lesions. The above lesions were both gradually improved by antituberculous chemotherapy with INH, RFP, and EB. He was finally diagnosed as posterior tuberculous spondylitis of the lumbar vertebra with cold abscess, and also clinically diagnosed as skull tuberculosis caused presumably by the inoculation of tubercle bacilli from the lumbar lesion by acupuncture.

[Mitral valve replacement and coronary artery bypass grafting for postinfarction mitral papillary muscle rupture]

A 79-year-old man was admitted to our hospital with heart failure following acute inferior myocardial infarction. An echocardiogram demonstrated severe mitral insufficiency, and coronary arteriography revealed double vesel disease. Following diagnosis of ischemic papillary muscle dysfunction, PTCA was performed, but the mitral insufficiency was not eliminated. Follow-up echocardiography disclosed rupture of the posterior papillary muscle. He underwent surgery on the 30th day after onset of acute myocardial infarction. Partial rupture of the posterior papillary muscle was found at surgery, and mitral valve replacement and single coronary artery bypass to Lcx were performed. His postoperative course was uneventful, and he was discharged on the 46th day after operation.

[A case of abdominal tuberculous lymphadenitis diagnosed by percutaneous needle biopsy under ultrasound control and followed up by ultrasound imaging]

A case of abdominal tuberculous lymphadenitis diagnosed by percutaneous needle biopsy under ultrasound control and followed up by ultrasound imaging was reported. A 63 years-old male was admitted to a certain hospital complaining of dizziness and diplopia. Chest roentgenogram showed bilateral infiltrative shadows in the upper lung fields and Mycobacterium tuberculosis was detected in cultures from specimens of gastric aspiration. Abdominal ultrasound examination and computed tomography showed abdominal lymph nodes swelling. Needle biopsy under ultrasound control was performed, and the specimens showed necrosis and Mycobacterium tuberculosis was positive by culture. He was diagnosed as lung tuberculosis with abdominal tuberculous lymphadenitis and admitted to our hospital for anti-tuberculous chemotherapy. Ultrasound examination done every two weeks showed diminution in size of the lymph nodes after a month of anti-tuberculous therapy. For the diagnosis of abdominal lymph node swelling, a needle biopsy under ultrasound control is safe and useful technique, and a ultrasound examination is also valuable to follow up the course of abdominal tuberculous lymphadenitis.

Effect of substrate on indirect immunofluorescence test for canine pemphigus foliaceus

The effect of substrate on indirect immunofluorescence (IIF) tests for the detection of circulating autoantibodies was studied by examining sera from 14 canine pemphigus foliaceus patients, six sera with non-pemphigus dermatoses and ten normal dog sera against five different substrates from three species. These substrates included bovine esophagus, bovine nose, bovine tongue, monkey esophagus, and canine nose skin. Nine out of 14 (64.3%) sera from patients with canine pemphigus foliaceus showed intercellular space staining by indirect immunofluorescence using bovine esophagus as substrate. However, sera from nonpemphigus dermatoses and normal dog did not react with bovine esophagus. In other substrates, only bovine tongue showed 1/8 (12.5%) positive reaction at the intercellular space by sera from canine pemphigus foliaceus. Dog nose skin showed the intercellular space staining against ten of ten (100%) normal dog serum. Monkey esophagus showed the fluorescent deposit at the intercellular space in four of nine (44.4%) of pemphigus foliacues dog sera, however, four of ten (40%) of normal dog sera revealed nonspecificity intercellular staining. These results indicate that the sensitivity and the specifity of IIF test in canine pemphigus foliaceus depend on the substrate. The best substrate for detecting circulating autoantibody in canine pemphigus foliaceus patients among five different substrates was bovine esophagus because of its sensitivity and high specificity. The diagnosis of canine pemphigus foliaceus should be made on the basis of a combination of clinical signs, histopathology, direct immunofluorescence, and the detection of circulating autoantibody.

Myosin light chain diphosphorylation is enhanced by growth promotion of cultured smooth muscle cells

The characteristics of actively growing smooth muscle cells (a variant, SM-3) were compared with those of growth-arrested cells with regard to response of myosin light chain (MLC) phosphorylation. Augmented MLC phosphorylation, in particular diphosphorylation, was observed in actively growing cells when stimulated with 30 microM prostaglandin F2alpha (PGF2alpha). The maximum level of diphosphorylation in growing cells was significantly higher than that in growth-arrested cells. The MLC diphosphorylation was sensitive to protein kinase C down-regulation by phorbol dibutylate and pretreatment by the protein kinase inhibitors, staurosporine (30 nM) and isoquinoline sulphonamide HA1077 (20 microM). The actively growing cells contained larger amounts of protein kinase C than growth-arrested cells. The phosphorylation sites of mono- and diphospho-MLC were determined to be MLC kinase-dependent sites (Thr18, Ser19). The PGF2alpha concentration/response curves of MLC diphosphorylation were shifted to the left and upwards in the presence of the protein phosphatase inhibitor calyculin A. These results suggest that PGF2alpha stimulation of actively growing SM-3 cells augments MLC kinase-dependent MLC diphosphorylation. Protein kinase C is involved indirectly in this reaction, possibly through MLC phosphatase-sensitive regulatory mechanisms.

Effects of KW-4679, a new orally active antiallergic drug, on antigen-induced bronchial hyperresponsiveness, airway inflammation and immediate and late asthmatic responses in guinea pigs

We investigated the effects of KW-4679, an antiallergic drug, on the development of bronchial hyperresponsiveness, airway inflammation and early and late asthmatic responses following aerosol antigen challenge in guinea pigs actively sensitized by the inhalation of aerosolized ovalbumin. Pretreatment with KW-4679 (10 mg/kg, p.o.) 1 h before antigen challenge prevented the development of bronchial hyperresponsiveness to inhaled methacholine. Examination of the bronchoalveolar lavage fluid 24 h after antigen challenge revealed the inhibitory effect of KW-4679 on the infiltration of eosinophils into the airway. Treatment with KW-4679 significantly inhibited both the immediate and late asthmatic responses. These results indicate that KW-4679 could be useful in the treatment of allergic diseases such as bronchial asthma.

Protective effects of ticlopidine and aspirin, administered alone and in combination, on thrombus formation in rat cerebral vessels

The protective effects of ticlopidine and d,l-lysine acetylsalicylate (L-ASA), used alone and in combination, on the pathogenesis of thrombosis in cerebral blood vessels were investigated in a rat animal model using a He-Ne laser method. Ticlopidine and L-ASA, given orally at a concentration from 100 mg/kg, inhibited thrombus formation in a dose-dependent manner. Ticlopidine (300 mg/kg p.o.) inhibited thrombosis in arterioles and venules for 3 days after administration. The inhibitory activity of L-ASA (300 mg/kg p.o.) was less prolonged than that of ticlopidine and was observed for only approximately 24 h. Combined administration of ticlopidine and L-ASA significantly enhanced and prolonged the antithrombotic effects of either drug given alone. The results demonstrate that ticlopidine and L-ASA have potent antithrombotic properties in rat cerebral blood vessels in vivo.

Roentgenographically occult small-cell lung cancer: case report and review of the literature

This report describes a rare case of roentgenographically occult small-cell lung cancer in a 73-year-old man with hemoptysis. Fiberoptic bronchoscopy disclosed a 5-mm dome-shaped lesion; a biopsy established the diagnosis of small-cell lung cancer. The patient received a combination of chemotherapy and radiotherapy. More than 10 years later, he is still alive without recurrent disease. A review of the literature of roentgenographically occult small-cell lung cancer revealed the following: (1) a history of heavy smoking was common; (2) double primary bronchogenic carcinoma was noted; (3) hemoptysis or bloody sputum was an initial common symptom; (4) the sensitivity of sputum cytologic analysis was relatively low; (5) the tumor, which was shiny, smooth, and covered with bronchial epithelium, was often located at the bifurcation; and (6) lymph node metastatic involvement occurred.

1,25-dihydroxyvitamin D3 differentiates normal neutrophilic promyelocytes to monocytes/macrophages in vitro

Although it is well established that the addition of 1,25-dihydroxyvitamin D3 (D3) to the culture of normal human granulocyte/macrophage progenitors induces monocyte/macrophage (Mo/M phi) colonies, the target cells of D3 in the Mo/M phi differentiation have not been identified. We examined whether neutrophilic promyelocytes are the target cells. As a source of the promyelocyte fraction, we used colonies after 5 days of culture (5-day colonies) of colony-forming unit-granulocyte. The culture contained granulocyte colony-stimulating factor (G-CSF) as the growth factor and generated only neutrophilic colonies. The promyelocytic nature of the 5-day colonies was confirmed morphologically, cytochemically, and ultrastructurally. After morphological evaluation on part of the individual colonies, they were transferred into new semisolid cultures with or without D3 (10(-7) mol/L) in the presence of G-CSF, then incubated for the subsequent 7 days. With D3, the colonies were loose, and all the constituent cells were morphologically small macrophages, which were positive for alpha-naphthyl butyrate (alpha NB) esterase, strongly positive for CD14 antigen, and plastic-adherent. While without D3, the colonies were rather compact, and all the constituent cells were morphologically mature neutrophils, which were positive for naphthol ASD-chloroacetate esterase and weakly positive for CD14 antigen. Secondary culture of the 8- or 10-day colonies with D3 induced a lower number of alpha NB-positive cells, in proportion to the percentage of promyelocytes at the time of transfer in each colony. Four days of secondary culture with D3 was sufficient to induce alpha NB-positive cells. G-CSF was not an essential factor to induce alpha NB-positive cells. These findings indicate that D3 differentiates normal human neutrophilic promyelocytes into the Mo/M phi lineage in vitro.

[Adjuvant chemotherapy for advanced gastric cancer]

For recent 40 years, many authors reported the results of adjuvant chemotherapy for advanced gastric cancer including 5-fluorouracil, uracil and tegafur, mitomycin C, cytosine arabinoside. OK-432 adriamycin, methotrexate, and cis-pltatin in solitary use of combinations. It is difficult to find a standard effective adjuvant chemotherapy for advanced gastric cancer in these reports. The reasons of this unclearness were as follows; (1) In phase III studies, surgery alone was not a control group in some reports. (2) The number of patients was too small to evaluate statistically. (3) Inter-institutional differences had important roles in the results of multicenter study in the other studies. For the future plans on adjuvant chemotherapy, it is important to make a simple designed protocol, and perform it as a multicenter study including institutions with minimum inter-institutional differences.

[Quantitative analysis of clinical usefulness of CRT monitor diagnosis by using previous and current chest images with simulated lung nodules]

We quantitatively evaluated the clinical usefulness of CRT diagnosis by using previous and current chest images with simulated lung nodules. Sixty normal chest X-ray films consisting of previous and current chest images were digitized. Simulated nodules prepared by a computer workstation were added on lung fields of the 30 current images. Observer performance tests were carried out with six radiologists to evaluate the detection of simulated lung nodules in CRT and hard copy film with previous and current images, and with only current films. ROC analyses indicated that the detection accuracy in CRT diagnosis with current and previous images was greater than that in CRT diagnosis with only a current image. In addition, there was no statistically significant difference between CRT and hard copy film diagnoses if current and previous images were employed for the diagnosis of simulated lung nodules. We believe that CRT diagnosis is as useful as hard copy film diagnosis for the evaluation of pulmonary nodules by using previous and current chest images.

[Effect of KW-4679, an antiallergic drug, on antigen-induced airway microvascular leakage in rats passively sensitized with mouse monoclonal IgE antibody]

We studied the effect of KW-4679, an antiallergic drug, on inhaled antigen-induced airway microvascular leakage in rats passively sensitized with mouse monoclonal IgE antibody. Inhaled antigen increased extravasation of Evans blue dye content in tracheal and main bronchus tissues. KW-4679 (0.3-10 mg/kg, p.o.) reduced antigen-induced microvascular leakage in trachea with an ED40 value of 4.9 mg/kg. KW-4679 also reduced antigen-induced microvascular leakage in main bronchus with an ED40 value of 0.47 mg/kg. The inhibitory effect of KW-4679 was more potent than those of ketotifen and terfenadine. These results suggest that KW-4679 clearly reduces airway microvascular leakage mediated by antigen-antibody reaction.

Cystic lesions of the maxillomandibular region: MR imaging distinction of odontogenic keratocysts and ameloblastomas from other cysts

OBJECTIVE

Differentiating odontogenic keratocysts and ameloblastomas from other cystic lesions in the maxillomandibular region is important because of their high recurrence rates. Conventional radiography, CT, and fine-needle aspiration biopsy are limited for differential diagnosis. The purpose of this study was to review the MR findings in patients with odontogenic keratocysts, ameloblastomas, and other maxillomandibular cysts to determine the value of MR imaging in the differential diagnosis of these lesions.

SUBJECTS AND METHODS

MR images were obtained in 38 patients with 43 cystic lesions of the maxillomandibular region. All the lesions (19 odontogenic keratocysts, 11 ameloblastomas, five primordial cysts, five radicular cysts, and three cysts of other types) were pathologically confirmed by surgery or biopsy. Contrast-enhanced MR studies were performed in 34 patients. Images were reviewed to determine various imaging parameters: locularity, solid or cystic pattern, thickness and contrast enhancement of the walls, and homogeneity and signal intensities of the fluids. T2 relaxation times of cystic components were calculated in 31 lesions.

RESULTS

MR images of odontogenic keratocysts showed that the cyst were unilocular in 10 lesions and multilocular in nine. In 10 lesions the cysts wall was uniformly thin and had poor contrast enhancement. Seven cysts had thick walls and two had no definite walls. In 17 lesions, the cystic contents showed heterogeneous signal intensity on T1-weighted images, T2-weighted images, or both. Eight cysts had predominantly intermediate or high T1-weighted signal intensity, and six cysts had predominantly intermediate T2-weighted signal intensity. MR findings in ameloblastomas were different from those in odontogenic keratocysts: a mixed solid and cystic pattern (11 lesions), irregularly thick walls (11 lesions), papillary projections (seven lesions), and strong enhancement of solid components (nine lesions). T2 relaxation times of cystic components were significantly shorter in odontogenic keratocysts than in ameloblastomas, with no overlap. All other cysts showed a unilocular, purely cystic pattern, with homogeneous fluids, although the T2 relaxation times of four lesions overlapped those of odontogenic keratocysts.

CONCLUSION

From the MR findings of the walls, solid components, and the fluid contents, odontogenic keratocysts could be differentiated from ameloblastomas in all cases, although some other cysts showed MR findings similar to those of odontogenic keratocysts.

[A case of volatile solvent psychosis accompanied with multiple neurological and psychological symptoms]

A case of psychosis accompanied with variable symptoms induced by chronic volatile solvent inhalation is reported in this study. The patient was a 27-year-old male who had abused volatile solvents for 15 years, and was sent to the hospital because of a tonic-clonic seizure. Severe psychomotor excitement was observed on the first day and the 7th day after admission. After 10 days of admission, we observed visual transformation and hyperthermia, which suggested acute toxic symptoms due to a volatile solvent. Furthermore, symptoms such as incoherence, delusions of persecution, and catalepsy were also observed in this case. There have been few reports of multiple neurological and mental symptoms appearing in cases of volatile solvent psychosis. Although we sometimes experience cases of solvent abuse with acute mental symptoms and recurrent excitement after sedation, such symptoms are not always observed because of flashback in the strict sense. Therefore, careful early treatment should be employed to prevent 'secondary excitement'.

[Changes in the working status of pulmonary tuberculosis patients after the admission]

We reported changes in the working status of pulmonary tuberculosis patients after the admission to our hospital. The age of patients ranged from 20 to 69 years old, and they were admitted to the 18th ward of our hospital from April 1991 to March 1993. We sent out the questionnaire to 198 patients, and the reply was sent back from 116 patients (Male 74, Female 42). Out of the 116 patients, we excluded the unemployed, the government employees, and self-employed workers. The remaining 76 patients were examined about their working status after admission, and the results were as follows: 2 patients lost their work, 11 patients retired from the work, 2 patients faced the drop of their position, and 3 patients had their salary reduced.

[Application of laser spectroscopy for 13C-breath tests]

A new device Tunable Diode Laser Spectroscopy (LS) was developed for the analysis of isotope ratios of 13CO2/12CO2. Its applicability for breath tests was validated. The exhaled breath is collected in a 2 l aluminum bag, of which CO2 is separated by cryogenic system and introduced into LS. Repeat measurements (8 times) of two kinds of gases (delta 13C:-2.62 and - 1.14%) revealed 0.045% and 0.065% variation (IS.D.), from which precision of measurement was estimated as 0.2% (3S.D.). Seven healthy volunteers were given orally different dose of 13C-glycine (50 mg-200 mg in 5 subjects) and 13C-methacetin (30 mg and 150 mg in 2 subjects). One patient with gastric ulcer with helicobacter pylori (HP) infection was given 100 mg of 13C-urea. Serial breath samples (9-15) were taken and measured both by LS and mass spectrometer (MS) thereafter. Appreciable peaks were obtained at 30-50 min. after glycine and methacetin ingestions. The height of the peaks were dose dependent. Increased excretion of 13CO2 characteristics to HP infection was obtained in 13C-urea breath test. Measured values with LS were identical with those measured with MS (60 samples) with the range of difference within 0.2% (3S.D.). [Y (LS) = 1.02X (MS) + 0.55, r = 0.996] We conclude the LS is suitable for various 13C-breath tests.

Inhibitory effects of TA-993, a new 1,5-benzothiazepine derivative, on platelet aggregation

TA-993, an l-cis 4',8-dimethyl derivative of the Ca2+ antagonist diltiazem, and some of its metabolites inhibited platelet aggregation induced by collagen, ADP, epinephrine, platelet activating factor, arachidonic acid, and U-46619 in human platelets in vitro. Among the metabolites, MB3 was the most potent (IC50, <1 micromol/L; several hundred times more potent than the parent compound). The d isomer of MB3 was >100 times less potent than the l isomer. Unlike acetylsalicylic acid (ASA), TA-993 inhibited both primary and secondary phases of ADP-induced platelet aggregation and also exhibited a disaggregating effect on human platelet aggregates. The inhibitory effect of TA-993 was enhanced when used in combination with ASA. In ex vivo studies involving rats, TA-993 (approximately 0.3 to 100 mg/kg PO) dose-dependently inhibited collagen-induced platelet aggregation (ED50, 3 mg/kg PO). In the whole-blood platelet aggregation system in rats, orally administered TA-993 was also inhibitory in single (3 to 30 mg/kg) or repeated daily (10 mg/kg per day for 10 days) dosage. Orally administered TA-993 dose-dependently inhibited ADP-induced platelet aggregation ex vivo in dogs (0.3 to 10 mg/kg), significantly protected mice against collagen + epinephrine-induced thromboembolic death (10 mg/kg), and inhibited thrombus formation in an arteriovenous shunt in rats (30 mg/kg). The Ca2+-antagonistic action of TA-993 was very weak in depolarized canine basilar arteries: the potency was approximately 1/10 that of diltiazem (d-cis) and d-TA-993. These results suggest that antiplatelet action is more characteristic of the l-cis than the d-cis 1,5-benzothiazepine structure and that TA-993 may become a clinically useful antiplatelet agent of this structure series.