The mechanism of oleic acid inhibiting platelet activation stimulated by collagen

BACKGROUND

Abnormal platelet activation is a key factor in the occurrence and development of thrombotic diseases. However, the physiological mechanisms that underlie platelet homeostasis remain unclear. Oleic acid, one of the most abundant lipids in the human diet, has potential antithrombotic effects. This study aimed to investigate the effects of oleic acid on platelet activation and thrombosis.

METHODS

Platelet aggregation, ATP release, and fibrinogen spread were evaluated to determine the role of oleic acid in platelet activation. A ferric chloride-induced carotid injury model was used to establish the effect of oleic acid on thrombus formation in vivo. Western blotting analysis and transfection experiments were performed to determine the mechanisms involved in this process.

RESULTS

Oleic acid inhibited platelet aggregation, granule release, and calcium mobilization. Furthermore, it inhibited the spread of platelets on fibrinogen. We also found that oleic acid delayed arterial thrombosis in mice, as demonstrated in a murine model of ferric chloride-induced carotid artery thrombosis. The molecular mechanism of its inhibition of platelet activity may be through the Syk-PLCγ2 and CaMKKβ/AMPKα/VASP pathways. In addition, we demonstrated that the phosphorylation of AMPK at Ser496 was an important mechanism of platelet activation.

CONCLUSIONS

Our study showed that oleic acid inhibits platelet activation and reduces thrombogenesis by inhibiting the phosphorylation of multiple signaling molecules, offering new insights into the research and development of antiplatelet drugs. Video Abstract.

The inhibitory effect of isoliquiritigenin on human platelets in vitro

Background

Platelets play important roles in several physiological and pathological processes. Multiple antiplatelet drugs have been developed for clinical practice. The active components of traditional Chinese medicine with antithrombotic effects are promising drugs to modulate platelet function. In our study, the antiplatelet effect of isoliquiritigenin (ILTG) and its mechanisms were examined.

Methods

Human platelet-rich plasma and a washed platelet suspension were prepared. Platelets were stimulated using collagen, thrombin, or adenosine diphosphate (ADP). The platelet lumi-aggregometer was applied to detect the aggregation of platelets and the release of adenosine triphosphate (ATP). The expression of P-selectin and the activation of integrin αIIbβ3 were detected using flow cytometry. The spreading of platelets on a fibrinogen-coated surface was visualized using immunofluorescent staining. The mechanisms of the antiplatelet effect were investigated using Western blotting.

Results

In this study, ILTG inhibited collagen- and thrombin-induced platelet aggregation, the release of dense granules and α-granules, and the activation of integrin αIIbβ3 in a dose-dependent manner. In addition, ILTG suppressed the spreading of platelets on immobilized fibrinogen. In collagen-activated platelets, ILTG markedly inhibited the expression of phosphorylation of phospholipase C gamma-2 (PLCγ2) and protein kinase B (Akt).

Conclusions

These results indicated that ILTG could inhibit the collagen- and thrombin-induced platelet aggregation and granule release via the glycoprotein VI-mediated signal pathway in vitro.

Anti-thrombotic effects mediated by dihydromyricetin involve both platelet inhibition and endothelial protection

Classical antithrombotics and antiplatelets are associated with high frequencies of bleeding complications or treatment failure when used as single agents. The platelet-independent fibrin generation by activated endothelium highlights the importance of vascular protection in addition to platelet inhibition in thrombosis prevention. Dihydromyricetin (DHM), the most abundant flavonoid in Ampelopsis grossedentata, has unique vasoprotective effects. This study aims to characterize the antithrombotic potential of DHM. The effects of DHM on the activation of platelets and endothelial cells were evaluated in vitro. Calcium mobilization and activation of mitogen-activated protein kinases (MAPKs) were examined as the potential targets of DHM based on molecular docking analysis. The in vivo effects of DHM were determined in FeCl3-injured carotid arteries and laser-injured cremasteric arterioles. The results showed that DHM suppressed a range of platelet responses including aggregation, secretion, adhesion, spreading and integrin activation, and inhibited exocytosis, phosphatidylserine exposure and tissue factor expression in activated endothelial cells. Mechanistically, DHM attenuated thrombin-induced calcium mobilization and phosphorylation of ERK1/2 and p38 both in platelets and endothelial cells. Intravenous treatment with DHM delayed FeCl3-induced carotid arterial thrombosis. Furthermore, DHM treatment inhibited both platelet accumulation and fibrin generation in the presence or absence of eptifibatide in the laser injury-induced thrombosis model, without prolonging ex vivo plasma coagulation or tail bleeding time. DHM represents a novel antithrombotic agent whose effects involve both inhibition of platelet activation and reduction of fibrin generation as a result of endothelial protection.

Incidence and impact of disseminated intravascular coagulation in COVID-19 a systematic review and meta-analysis

OBJECTIVES

Coronavirus disease 2019 (COVID-19) is a novel infectious disease, with significant morbidity and mortality. This meta-analysis is to evaluate the prevalence of disseminated intravascular coagulation (DIC) in COVID-19 patients and to determine the association of DIC with the severity and prognosis of COVID-19.

METHODS

We searched the PubMed, EMBASE, and China National Knowledge Infrastructure (CNKI) database until August 12, 2020. The meta-analysis was performed using Stata 16.0 software.

RESULTS

14 studies were included in our meta-analysis. The pooled analysis revealed that the incidence of COVID-19 patients developing DIC was 3% (95%: 1%-5%, P < 0.001). In addition, deaths were more likely to be associated with DIC (Log OR = 2.46, 95% CI: 0.94-3.99, P < 0.001) with statistical significance.

CONCLUSIONS

DIC is associated with the severity and poor prognosis of COVID-19 patients. Therefore, attention should be paid to coagulation dysfunction in COVID-19 patients. Monitoring of coagulation indicators may improve the prognosis of COVID-19 inpatients.

Characteristics of mortal COVID-19 cases compared to the survivors

The outbreak of coronavirus disease 2019 (COVID-19) initially occurred in December 2019 and triggered a public health emergency. The increasing number of deaths due to this disease was of great concern. Therefore, our study aimed to explore risk factors associated with COVID-19 deaths.

After having searched the PubMed, EMBASE, and CNKI for studies published as of August 10, 2020, we selected articles and extracted data. The meta-analysis was performed using Stata 16.0 software.

Nineteen studies were used in our meta-analysis. The proportions of comorbidities such as diabetes, hypertension, malignancies, chronic obstructive pulmonary disease, cardio-cerebrovascular disease, and chronic liver disease were statistically significantly higher in mortal COVID-19 cases. Coagulation and inflammatory markers, such as platelet count, D-dimer, prothrombin time, C-reactive protein, procalcitonin, and interleukin 6, predicted the deterioration of the disease. In addition, extracorporeal membrane oxygenation and mechanical ventilation predicted the poor prognosis during its progression.

The COVID-19 pandemic is still evolving, placing a huge burden on healthcare facilities. Certain coagulation indicators, inflammatory indicators, and comorbidities contribute to the prognosis of patients. Our study results may help clinicians optimize the treatment and ultimately reduce the mortality rate.

The long non-coding RNA PVT1/miR-145-5p/ITGB8 axis regulates cell proliferation, apoptosis, migration and invasion in non-small cell lung cancer cells

Lung cancer is one of the leading causes of death worldwide and non-small cell lung cancer (NSCLC) accounts for approximately 80% of lung cancer. Long noncoding RNAs (lncRNAs) are closely associated with the development and progression of various cancers, including lung cancer. The purpose of this study was to explore the potential role and molecular mechanism of lncRNA plasmacytoma variant translocation 1 (PVT1) in regulating the proliferation, apoptosis, migration, and invasion of NSCLC cells. The expressions of PVT1, integrin β-8 (ITGB8), and miR-145-5p were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of ITGB8, MEK, p-MEK, ERK, and p-ERK were measured by western blot analysis. Cell proliferation, apoptosis, migration, and invasion were determined by MTT assay, flow cytometry, and transwell assay, respectively. The potential binding sites between miR-145-5p and PVT1 or ITGB8 were predicted by online software and verified by luciferase reporter assay. A xenograft tumor model was established to confirm the effect of PVT1 on NSCLC in vivo. We found out that the expression levels of PVT1 and ITGB8 were upregulated in NSCLC tissues and cells. Knockdown of PVT1 or ITGB8 suppressed cell proliferation, migration, invasion and promoted apoptosis in NSCLC cells, which could be reversed by ITGB8 overexpression in NSCLC cells. Moreover, PVT1 could regulate ITGB8 expression via direct binding to miR-145-5p. Furthermore, PVT1 regulated the MEK/ERK pathway by affecting ITGB8 expression. In addition, knockdown of PVT1 inhibited tumor growth, ITGB8 expression, MEK/ERK signaling pathway, and increased miR-145-5p expression in vivo. In conclusion, the knockdown of PVT1 inhibited proliferation, migration, and invasion but induced apoptosis of NSCLC cells by regulating miR-145-5p/ITGB8 axis and inhibiting MEK/ERK signaling pathway, providing a novel avenue for the treatment of NSCLC.

Inhibition of keratinocyte necroptosis mediated by RIPK1/RIPK3/MLKL provides a protective effect against psoriatic inflammation

Psoriasis is a common autoimmune and chronic inflammatory skin disorder globally affecting 0.51–11.43% of adults. Inflammation-associated cell death in keratinocytes plays a key role in the process of integrate inflammatory cascade in psoriasis. Necroptosis is a regulated necrotic cell death mediated by receptor interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like pseudokinase (MLKL), which participates in many human inflammatory diseases. However, the mechanism and function of programmed necrosis in psoriasis is not well-illustrated. In the current study, we provide evidence for the involvement of necroptosis in psoriasis. RIPK1 and MLKL were significantly upregulated and localized in all layers of the epidermis in human psoriatic lesions, while RIPK3 and phosphorylated MLKL were mainly expressed in keratinocytes, which located in the upper layers. Increased tendency of necroptosis was also found in IMQ-induced psoriasiform skin of mice. Further, we discovered that both the inhibitor of RIPK1 R-7-Cl-O-Necrostatin-1 (Nec-1s) and MLKL-inhibitor necrosulfonamide (NSA) suppressed necroptosis in HaCaT cells and IMQ mouse models, powerfully blocked IMQ-induced inflammatory responses in vivo, and significantly downregulated the production of inflammatory factors like IL-1β, IL-6, IL-17A, IL-23a, CXCL1, and CCL20. These findings promote the development of new therapies for the treatment of necroptosis-activated pathologies for psoriasis.

Ten-eleven Translocation-2 Regulates DNA Hydroxymethylation Status and Psoriasiform Dermatitis Progression in Mice

Epigenetics plays an important role in the development and progression of many diseases. There is increasing evidence for the importance of epigenetic modifications in the progression of psoriasis. The aim of this study was to examine the role and potential mechanism of action of 5-hydroxymethylcytosine (5-hmC) and ten-eleven translocation-2 (TET2) in psoriasiform dermatitis in mice. Immunohistochemical staining was performed on psoriasis patients and healthy controls. Topical application of imiquimod cream to the dorsal skin of mice was used to induce psoriasiform dermatitis. In comparison with healthy controls, 5-hmC was more extensive and intense in the skin lesions from psoriasis patients. TET2 and 5-hmC were highly expressed in imiquimod-induced psoriasiform skin lesions. Importantly, knockdown of TET2 expression in mice attenuated the psoriasiform phenotype and the expression levels of proinflammatory cytokines (interleukin-17A and -17F and interferon-?) and the chemokine CXCL1 in the lesional skin of mice. This is the first demonstration of a critical role for TET2 in psoriasiform dermatitis in a mouse model, and indicates that 5-hmC may serve as a potential biomarker of psoriasis.

Resolvin D1 attenuates imiquimod-induced mice psoriasiform dermatitis through MAPKs and NF-κB pathways

BACKGROUND

Resolvin D1 (RvD1), a pro-resolution lipid mediator derived from docosahexaenoic acid (DHA), has been described to promote several kinds of inflammatory resolution. However, the effects and anti-inflammatory mechanisms of RvD1 on psoriasis have not been previously reported.

OBJECTIVE

The present study aimed to determine the protective effects and the underlying mechanisms of RvD1 on imiquimod (IMQ)-induced psoriasiform dermatitis.

METHODS

Mice were topically treated with IMQ to develop psoriasiform dermatitis on their shaved back, pretreated intraperitoneally (i.p.) with or without RvD1 or tert-butoxycarbonyl Met-Leu-Phe peptide (Boc), a lipoxin A4 (ALX) receptor antagonist. The severity was monitored and graded using a modified human scoring system, the Psoriasis Area and Severity Index (PASI), histopathology, and the signature cytokines of psoriasis (IL-23, IL-17, IL-22 and TNF-α). The mRNA and protein levels of inflammatory cytokines were quantified by quantitative real-time PCR (QRT-PCR) and ELISA. The expressions of signaling proteins MAPKs and NF-κB p65 were analyzed using western blotting. Electrophoretic mobility shift assay (EMSA) was used to check NF-κB p65 DNA binding activity.

RESULTS

Our study showed that RvD1 alleviated IMQ-induced psoriasiform dermatitis and improved skin pathological changes. RvD1 markedly inhibited IMQ-induced activation of ERK1/2, p38, JNK (c-Jun N-terminal protein kinase, a subfamily of MAPKs), and NF-κB. Furthermore, pretreatment with Boc, would not exacerbate skin inflammation of IMQ-induced mice, but significantly reversed the beneficial effects of RvD1 on IMQ-induced psoriasiform inflammation.

CONCLUSION

RvD1 can obviously improve skin inflammation in IMQ-induced mice psoriasiform dermatitis. The protective mechanisms might be related to its selective reaction with lipoxin A4 receptor/Formyl-peptide receptor 2 (ALX/FPR2), by downregulating relevant cytokines of the IL-23/IL-17 axis expression, the inhibition of MAPKs and NF-κB signaling transduction pathways. Thus, these results show that RvD1 could be a possible candidate for psoriasis therapy.

Lipoxin A4 and its analog suppress inflammation by modulating HMGB1 translocation and expression in psoriasis

Psoriasis is a chronic inflammatory skin disease that affects 2-3% of the global population, and there is still no known possibility of a cure. Lipoxin A4 (LXA4), an endogenous lipoxygenase-derived eicosanoid mediator, has potent dual pro-resolving and anti-inflammatory properties. BML-111 (5(S)-6(R)-7-trihydroxyheptanoic acid methyl ester), a lipoxin receptor agonist, has been previously confirmed to be equivalent to LXA4 in the anti-inflammatory processes. High mobility group box 1 (HMGB1) serves as an inflammatory cytokine when secreted extracellularly in psoriatic lesions and is involved in the development of psoriasis. Therefore, we investigated the effects of LXA4 and BML-111 on the HMGB1 signaling cascade and inflammation in lipopolysaccharide (LPS)-induced keratinocytes and imiquimod (IMQ)-induced psoriasiform dermatitis in mice. In the present study, we found that treatment with BML-111 attenuated the development of IMQ-induced psoriasiform dermatitis. Furthermore, treatment with BML-111 and LXA4 inhibited HMGB1 translocation from the nucleus to cytoplasm and downregulated the expression of toll-like receptor 4 (TLR4), receptor for advanced glycation end products (RAGE), p-ERK1/2, nuclear NF-κB p65, and proinflammatory cytokines in vivo and in vitro. Our findings indicate that LXA4 and its analog may be potential therapeutic candidates for psoriasis because of their ability to modulate the translocation and expression of HMGB1.

Curcumin alleviates diabetic cardiomyopathy in experimental diabetic rats

Objectives

Diabetic cardiomyopathy (DCM), characterized by myocardial structural and functional changes, is an independent cardiomyopathy that develops in diabetic individuals. The present study was sought to investigate the effect of curcumin on modulating DCM and the mechanisms involved.

Methods

An experimental diabetic rat model was induced by low dose of streptozoticin(STZ) combined with high energy intake on rats. Curcumin was orally administrated at a dose of 100 or 200 mg·kg⁻¹·d⁻¹, respectively. Cardiac function was evaluated by serial echocardiography. Myocardial ultrastructure, fibrosis area and apoptosis were assessed by histopathologic analyses. Metabolic profiles, myocardial enzymes and oxidative stress were examined by biochemical tests. Inflammatory factors were detected by ELISA, and interrelated proteins were measured by western blot.

Results

Rats with DCM showed declined systolic myocardial performance associated with myocardial hypertrophy and fibrosis, which were accompanied with metabolism abnormalities, aberrant myocardial enzymes, increased AGEs (advanced glycation end products) accumulation and RAGE (receptor for AGEs) expression, elevated markers of oxidative stress (MDA, SOD, the ratio of NADP⁺/NADPH, Rac1 activity, NADPH oxidase subunits expression of gp91^phox and p47^phox ), raised inflammatory factor (TNF-α and IL-1β), enhanced apoptotic cell death (ratio of bax/bcl-2, caspase-3 activity and TUNEL), diminished Akt and GSK-3β phosphorylation. Remarkably, curcumin attenuated myocardial dysfunction, cardiac fibrosis, AGEs accumulation, oxidative stress, inflammation and apoptosis in the heart of diabetic rats. The inhibited phosphorylation of Akt and GSK-3β was also restored by curcumin treatment.

Conclusions

Taken together, these results suggest that curcumin may have great therapeutic potential in the treatment of DCM, and perhaps other cardiovascular disorders, by attenuating fibrosis, oxidative stress, inflammation and cell death. Furthermore, Akt/GSK-3β signaling pathway may be involved in mediating these effects.

Basis of the gabamimetic profile of ethanol

This article summarizes the proceedings of a symposium held at the 2005 Research Society on Alcoholism meeting. The initial presentation by Dr. Wallner provided evidence that selected GABA(A) receptors containing the delta subunit display sensitivity to low intoxicating ethanol concentrations and this sensitivity is further increased by a mutation in the cerebellar alpha6 subunit, found in alcohol-hypersensitive rats. Dr. Mameli reported that ethanol affects gamma-aminobutyric acid (GABA) function by affecting neural circuits that influence GABA release. Dr. Parsons presented data from electrophysiological and microdialysis investigations that ethanol is capable of releasing GABA from presynaptic terminals. Dr. Morrow demonstrated that systemic ethanol increases neuroactive steroids in brain, the absence of which alters various functional responses to ethanol. Dr. Criswell presented evidence that the ability of ethanol to increase GABA was apparent in some, but not all, brain regions indicative of regional specificity. Further, Dr. Criswell demonstrated that neurosteroids alone and when synthesized locally by ethanol act postsynaptically to enhance the effect of GABA released by ethanol in a region specific manner. Collectively, this series of reports support the GABAmimetic profile of acutely administered ethanol being dependent on several specific mechanisms distinct from a direct effect on the major synaptic isoforms of GABA(A) receptors.

Effects of WIN 55,212-2 on I(K) current in cultured trigeminal ganglion neurons of rat

To investigate the effects of WIN 55,212-2 on I(K) in cultured rat trigeminal ganglion (TG) neurons, whole-cell patch clamp techniques were used to record the I(K) before and after WIN 55,212-2 perfusion at different concentrations. 30 micromol/L WIN 55,212-2 markedly (35.7% +/- 7.3%, P < 0.01, n = 8) inhibited I(K) currents, and the currents were partially recovered after washing. 30 micromol/L WIN 55,212-2 also induced a significant depolarizing shift in conductance-voltage parameters (control: V0.5 = 10.43 +/- 4.25 mV, k = 16.27 +/- 3.86; WIN 55,212-2: V0.5 = 24.71 +/- 3.91 mV, k =16.69 +/- 2.75; n = 8, P < 0.01 for V0.5). 0.01 micromol/L WIN 55,212-2 slightly (27.0% +/- 7. 9%, P < 0.05, n = 7) increased I(K) currents, but had no significant change in conductance voltage parameters (control: V0.5 =10.74 +/- 5.27 mV, k = 17.33 +/- 2.96; WIN 55,212-2: V0.5 = 11.06 +/- 2.05 mV, k = 19.69 +/- 6.60; n = 7, P > 0.05 for V0.5 and k). These results suggested that WIN 55,212-2 has dual action, which might be through different receptors.

Effect of berberine on the mRNA expression of nitric oxide synthase (NOS) in rat corpus cavernosum

In order to further investigate the mechanisms of action of berberine (Ber), we assessed the effects of Ber on the mRNA expression of nitric oxide synthases (NOS) in rat corpus cavernosum. After incubation with Ber for 1 or 3 h respectively, the levels of NOS mRNA were examined by reverse transcription polymerase chain reaction (RT-PCR). Our results showed that there were iNOS and eNOS mRNA expressions in rat corpus cavernosum. Ber enhanced eNOS mRNA expression in rat penis, but exhibited no effect on the expression of iNOS mRNA (P > 0.05). The present study indicated that the relaxation of Ber involved the NO-cGMP signal transduction pathway. The enhancing effect of Ber on eNOS mRNA expression might associated with its relaxation of corpus cavernosum.

Differential modulation of GABA- and NMDA-gated currents by ethanol and isoflurane in cultured rat cerebral cortical neurons

Ethanol and the volatile anesthetics share many features including effects on both GABA and NMDA receptors. To determine the degree of similarity between these compounds, we examined the concentration-response curves for ethanol and isoflurane on currents gated by GABA or NMDA. The effects of isoflurane and ethanol on the righting reflex of rats were also observed. The concentration of ethanol causing loss of the righting reflex of rats was 82.3+/-2.9 mM, whereas median concentration of isoflurane exerting that effect was 0.125 mM. Both isoflurane and ethanol inhibited NMDA-gated currents in cultured cerebral cortical neurons at concentrations well below those associated with loss of the righting reflex or anesthesia. However, the effect of isoflurane was greater than that of ethanol and the slope of the concentration-response curve for isoflurane less steep than that for ethanol. Isoflurane enhanced GABA-gated currents at anesthetic concentrations but there was a sharp concentration-response curve with only minimal effects of isoflurane on GABA-gated currents at concentrations associated with loss of the righting reflex. In contrast, ethanol had no effect on GABA-gated currents even at lethal concentrations, i.e. 300 mM or 1.2%. Comparison of the concentration-response curves for the effects of isoflurane on NMDA- and GABA-gated currents has revealed both EC50 and Hill slope for the potentiation of GABA-gated currents were significantly greater than those for inhibition of NMDA-gated currents. These results support the hypothesis that isoflurane has actions on both the GABA and NMDA systems that are not shared by ethanol.

Intrahepatic adenosine triggers a hepatorenal reflex to regulate renal sodium and water excretion

The mechanism for water and sodium retention in liver cirrhosis is related to the disturbance in hepatic portal circulation. We hypothesize that the increases in intraportal adenosine, which occur when the portal blood flow decreases, may trigger the hepatorenal reflex to inhibit renal water and sodium excretion. In anesthetized rats, intravenous vs. intraportal adenosine-induced effect on renal water and sodium excretion was compared in normal animals and animals with hepatic or renal denervation, and in the presence of an adenosine receptor antagonist. Compared to saline infusion, intraportal adenosine (0.02 mg kg(-1) min(-1) for 1 h) infusion decreased urine flow by 51.3% (11.7 +/- 2.3 vs. 5.7 +/- 0.5 microl min(-1)) for the first 30 min and by 49% (22.8 +/- 5.4 vs. 11.6 +/- 1.5 microl min(-1)) for the second 30-min duration. Urinary sodium excretion was also decreased. Intraportal administration of an adenosine receptor antagonist (8-phenyltheophylline (8-PT), 3 mg kg(-1) bolus injection followed by 0.05 mg kg(-1) min(-1) continuous infusion), as well as liver or kidney denervation, abolished adenosine-induced inhibition. In contrast, intravenous adenosine infusion had no influence on either urine flow or sodium excretion. The data indicated that selectively increased intraportal adenosine inhibited renal water and sodium excretion. The water and sodium retention commonly seen in the hepatorenal syndrome may be related to intraportal adenosine accumulation due to the decrease in intraportal portal flow.

Modeling of branching structures of plants

Previous studies of branching structures generally focused on arteries. Four cost models minimizing total surface area, total volume, total drag and total power losses at a junction point have been proposed to study branching structures. In this paper, we highlight the branching structures of plants and examine which model fits data of branching structures of plants the best. Though the effect of light (e.g. phototropism) and other possible factors are not included in these cost models, a simple cost model with physiological significance, needs to be verified before further research on modeling of branching structures is conducted. Therefore, data are analysed in this paper to determine the best cost model. Branching structures of plants are studied by measuring branching angles and diameters of 234 junctions from four species of plants. The sample includes small junctions, large junctions, two- and three-dimensional junctions, junctions with three branches joining at a point and those with four branches joining at a point. First, junction exponents (x) were determined. Second, log-log plots indicate that model of volume minimization fits data better than other models. Third, one-sided t -tests were used to compare the fitness of four models. It is found that model of volume minimization fits data better than other cost models.

Studies on the synthesis of N(G)-nitro-L-arginine derivatives and their effects on septic shock

(HCl x N(G)-NO2-Arg)2Lys-OCH3, (HCl x N(G)-NO2-Arg)2Lys-OH, [(HCl x N(G)-NO2-Arg)2Lys]2Lys-OCH3, and [(HCl x N(G)-NO2-Arg)2Lys]2Lys-OH were synthesized by use of a solution method. Their effect on septic shock was studied in vivo. The results indicate that increasing the number of N(G)-NO2-Arg residues in a molecule may be useful to improve the response to septic shock.

Synthesis of RGD containing peptides and their vasodilation effect

APLRV, SLRR, RGDS, and RGDF were synthesized by use of the solution method via the corresponding protective intermediates. After fragment condensation and deprotection, APLRVRGDS, APLRVRGDF, SLRRRGDS, and SLRRRGDF were obtained. The effect of these RGD containing peptides on rat aortic strips pretreated with noradrenaline (NE) were observed. The relaxing extents of contracted strips for them at three doses (10(-5) mol/L, 10(-6) mol/L and 10(-7) mol/L) indicated that, in a few cases, this kind of combination of these fragments may enhance the desirable activity.

Synthesis and analgesic activity of N,N'-dicarbonyltryptamines

5-Methoxytryptamine and L-tryptophan methyl ester were acylated with malonic acid, dimethyl malonate, or succinic anhydride to produce the corresponding N,N'-dicarbonyltryptamine derivatives. The analgesic activity was evaluated by the tail flick test. All of the compounds exhibited desirable analgesic potency. This result is consistent with that of N-(N-acetyl-L-tryptophanyl)-5-methoxytryptamine and confirmed that introducing substituted tryptamine into the amide chain of melatonin does enhance analgesic potency.

Synthesis and analgesic activity of N-(N-acetyl-L-amino-acyl)-5-methoxytryptamines

5-Methoxytryptamine was acylated with N-acetyl-L-amino acids to give rise the corresponding N-(N-acetyl-L-amino acyl)-5-methoxytryptamines. The analgesic activity was evaluated by the tail flick test. Among the 6 compounds, the analgesic potency of N-(N-acetyl-tryptophanyl)-5-methoxytryptamine (5e) and N-(N-acetyl-glycyl)-5-methoxytryptamine (5a) are much more potent than that of melatonin.

Nitric oxide mediates hepatic arterial vascular escape from norepinephrine-induced constriction

The involvement of nitric oxide (NO) in the vascular escape from norepinephrine (NE)-induced vasoconstriction was investigated in the hepatic arterial vasculature of anesthetized cats. The hepatic artery was perfused by free blood flow or pump-controlled constant-flow, and NE (0.15 and 0.3 microg x kg(-1) x min(-1), respectively) was infused through the portal vein. In the free-flow perfusion model, the NE-induced hepatic vasoconstriction recovered from the maximum point of the constriction, resulting in 36.6 +/- 5. 9% vascular escape. Blockade of NO formation with N(omega)-nitro-L-arginine methyl ester (L-NAME, 2.5 mg/kg ipv) potentiated NE-induced maximum vasoconstriction, and the potentiation was reversed by L-arginine (75 mg/kg ipv). Furthermore, NE-induced vasoconstriction became more stable after L-NAME, resulting in an inhibition of vascular escape (7.5 +/- 3.3%), and the inhibition was reversed by L-arginine (23.0 +/- 6.4%). Similar potentiation of NE-induced vasoconstriction and inhibition of hepatic vascular escape by L-NAME (40.4 +/- 4.3% control vs. 10.2 +/- 3.7% post-L-NAME escape) and the reversal by L-arginine were also observed in the constant-flow perfusion model. The data suggest that NO is the major endogenous mediator involved in the hepatic vascular escape from NE-induced vasoconstriction.

Nitric oxide inhibits norepinephrine-induced hepatic vascular responses but potentiates hepatic glucose output

We previously reported that sympathetic nerve-induced vasoconstriction in the intestine resulted in shear stress induced release of nitric oxide (NO) that led to presynaptic inhibition of transmitter release. In contrast, studies in the liver suggested a postsynaptic inhibition of vascular responses, thus leading to the hypothesis tested here that maintained catecholamine release in the liver would result in maintained metabolic catecholamine action in the face of inhibition of vascular responses. In rats, norepinephrine (NE) induced elevations in arterial glucose content were inhibited by NO synthase antagonism (N(omega)-nitro-L-arginine methyl ester (L-NAME), 10 mg/kg, intraportal) but potentiated by NO donor administration (3-morpholinosydnonimine (SIN-1), 0.2 mg/kg, intraportal). The potentiated effect of SIN-1 was abolished by indomethacin (7.5 mg/kg, intraportal). To confirm the hepatic site of metabolic effect, cats were used so that blood flow and hepatic glucose balance could be determined. SIN-1 potentiated NE-induced glucose output from the liver from 5.0 +/- 0.4 to 7.2 +/- 0.6 mg x min(-1) x kg(-1). The potentiation was blocked by methylene blue, a guanylate cyclase inhibitor. Contrary to the glucose response, L-NAME potentiated but SIN-1 attenuated NE-induced portal vasoconstriction. Thus NO is shown to produce differential modulation of vascular and metabolic effects of NE. Vasoconstriction of the hepatic vasculature is inhibited by NO, whereas the glycogenolytic response to NE is potentiated, responses that are probably mediated by prostaglandin.

Interactive role for neurosteroids in ethanol enhancement of gamma-aminobutyric acid-gated currents from dissociated substantia nigra reticulata neurons

Although previous in vivo electrophysiological studies demonstrated a consistent ethanol enhancement of gamma-aminobutyric acid (GABA) responsiveness from substantia nigra reticulata (SNR) neurons, ethanol applied in vitro to dissociated neurons from the SNR had an inconsistent effect on GABA function. One source for the disparity between these contrasting in vivo and in vitro results could be an endogenous factor (acting on an auxiliary site on GABA(A) receptors) that was not available to the isolated SNR neurons. Because neurosteroids are present in vivo and act on an auxiliary site, it was hypothesized that the presence of a neurosteroid was important for a consistent effect of ethanol on GABA responsiveness from neurons studied in vitro. Alone, the neurosteroid analog alphaxalone produced a significant, concentration-related enhancement of GABA responsiveness from isolated SNR neurons. In contrast to an inconsistent action of 100 mM ethanol on GABA responsiveness in the absence of alphaxalone, the presence of 30 and 100 nM alphaxalone resulted in the majority of isolated neurons responding to this ethanol level. At a concentration of alphaxalone as low as 30 nM, ethanol produced a robust concentration-related increase in GABA-gated currents from this cell type. The neurosteroid 3alpha, 5alpha-tetrahydrodeoxycorticosterone (100 nM) also permitted a reliable concentration-dependent ethanol enhancement of responses to GABA from SNR cells, indicative that the effects of alphaxalone were not unique. This consistent neurosteroid-induced ethanol enhancement of GABA responsiveness from dissociated SNR neurons supports the view that neurosteroids may play a key role in the action of ethanol on postsynaptic GABA(A) receptor function.

Contribution of endogenous endothelin to large epicardial coronary artery tone in dogs and humans

Nitric oxide (NO) may normally impair endothelin (ET) activity in epicardial coronary arteries. Lifting this inhibitory feedback could reveal ET-dependent effects involving ET(A)- and/or ET(B)-receptor activation. In conscious dogs, the blockade of ET(A) receptors (intracoronary Ro-61-1790) increased external circumflex coronary artery diameter (CD) (sonomicrometry) by 0.10 +/- 0.01 from 3.04 +/- 0.12 mm (P < 0.01) without altering coronary blood flow (Doppler). Similarly, CD increased (0.09 +/- 0.01 from 2.91 +/- 0.14 mm; P < 0. 01) when Ro-61-1790 was given after blockade of NO formation with intracoronary N(omega)-nitro-L-arginine methyl ester (L-NAME). In contrast, ET(B)-receptor blockade (intracoronary Ro-46-8443) did not influence baseline CD with and without L-NAME. In vitro, increases in tension caused by N(omega)-nitro-L-arginine (L-NNA) or PGF(2alpha) in arterial rings were reduced by ET(A)- but not ET(B)-receptor blockade. ET(A)-receptor blockade also reduced the increase in tension caused by L-NNA in human coronary arterial rings. Thus ET(A) receptors, but not ET(B) receptors, account for ET-dependent constriction in canine epicardial coronary arteries in vivo. ET-dependent effects were independent of the level of NO formation in vitro and in vivo. In human epicardial coronary arterial rings, ET(A)-receptor blockade also caused significant relaxation.

Blood flow-dependent prostaglandin f(2alpha) regulates intestinal glucose uptake from the blood

Intestinal glucose uptake (GUi) from blood increased when blood flow (BF) was increased. The increase in BF could elevate shear stress. Therefore, we hypothesize that shear stress-induced release of autacoids mediates the increase in GU(i). A surgically separated segment of small intestine was perfused in situ with the use of an arterial circuit in anesthetized cats. Arterial and portal blood samples were taken simultaneously for assessment of GU(i). Adenosine was used to elevate intestinal BF. The GU(i) increased by 45.0 +/- 18.3 from 25.3 +/- 3.8 micromol. min(-1). 100 g tissue(-1) when the BF increased about four times. It was not a direct effect of adenosine because GU(i) was not altered if the flow was held constant. This increase was blocked by a cyclooxygenase inhibitor, indomethacin, but not by nitric oxide synthase blocker N(G)-nitro-L-arginine methyl ester. Furthermore, prostaglandin F(2alpha) (PGF(2alpha)) but not PGE(2) or PGI(2) reversed the blockade of the increase in GU(i) after indomethacin during elevated blood flow, whereas they had no influence on basal uptake. The results suggest that shear stress-induced release of PGF(2alpha) mediated the increase in GU(i) when blood flow was elevated.

Shear stress-induced nitric oxide antagonizes adenosine effects on intestinal metabolism

The influence of nitric oxide (NO) on adenosine-induced metabolic effects was studied in the intestine. Blood flow supplied an in situ- isolated segment of small intestine in anesthetized cats via the superior mesenteric artery (SMA) and was controlled by a vascular circuit. The SMA and portal samples were taken for analysis of oxygen and lactate. Adenosine (0.4 mg. kg-1. min-1, intra-SMA) reduced oxygen consumption by 25.1 +/- 2.9 from 73.1 +/- 10.8 micromol. min-1. 100 g-1 and increased lactate production by 13.3 +/- 3.0 from 12.8 +/- 4.6 micromol. min-1. 100 g tissue-1 during constant-flow (CF, decreased shear stress) but not during constant-pressure (CP, increased shear stress) perfusion. Blockade of NO synthase using Nomega-nitro-L-arginine methyl ester did not affect the metabolic effects of adenosine during CF but eliminated the differences seen between CP and CF perfusion. A NO donor, 3-morpholinosydnonimine, attenuated the metabolic effects of adenosine during CF perfusion. The results suggested that shear-induced NO antagonized metabolic effects of adenosine but that the inhibition of vascular effects by NO was not shear dependent since it occurred in both CP and CF perfusion.

Endothelin-dependent tone limits acetylcholine-induced dilation of resistance coronary vessels after blockade of NO formation in conscious dogs

Nitric oxide (NO) impairs endothelin (ET) formation and/or action in isolated vessels. We hypothesized that ET may magnify the consequences of NO formation blockade on receptor-operated dilation of resistance coronary vessels in conscious dogs. In conscious instrumented dogs, graded intracoronary (IC) doses of acetylcholine (ACh) were delivered before IC administration of Nomega-nitro-L-arginine methyl ester (L-NAME), after L-NAME, and after L-NAME plus IC bosentan, an ETA/ETB receptor blocker. Before L-NAME, ACh (100 ng. kg-1. min-1) increased coronary blood flow (CBF) by 43+/-4% from 47+/-6 mL. min-1. After L-NAME, ACh failed to increase CBF (-3+/-2% from 50+/-7 mL. min-1). CBF responses to ACh were partially restored (+10+/-2% from 50+/-7 mL. min-1, P<0.01) after the addition of bosentan. Bosentan alone (without L-NAME) did not alter CBF responses to ACh. Blockade of ETA (Ro 61-1790) but not ETB (Ro 46-8443) receptors partially restored CBF responses to ACh after L-NAME. Myocardial immunoreactive ET levels in the perfusion territories of the circumflex and left anterior descending coronary arteries did not differ. ETA-dependent tone magnified the inhibitory effects of blockade of NO formation on receptor-operated dilation to ACh in resistance coronary vessels. Presumably, stimulated NO release has an inhibitory action on endogenous ET production and/or action at the level of resistance coronary vessels.

Nitric oxide-independent dilation of conductance coronary arteries to acetylcholine in conscious dogs

NO and prostacyclin formation cannot entirely account for receptor-operated endothelium-dependent dilation of coronary vessels, since vasodilator responses are not completely suppressed by inhibitors of these agents. Therefore, we considered that another factor, such as an endothelium-derived hyperpolarizing factor described in vitro, may participate in NO- and prostacyclin-independent coronary dilator responses. In conscious instrumented dogs, intracoronary acetylcholine (ACh, 30.0 ng.kg-1.min-1) increased the external epicardial coronary diameter (CD) by 0.18 +/- 0.03 mm (from 3.44 +/- 0.11 mm) when increases in coronary blood flow (CBF) were prevented and increased the CD by 0.20 +/- 0.05 when CBF was allowed to increase. After the administration of intracoronary N omega-nitro-L-arginine methyl ester (L-NAME), CBF responses to ACh were abolished, but CD responses (0.23 +/- 0.05 from 3.22 +/- 0.09 mm) were maintained. Blockade of NO formation was confirmed by reduced CD baselines and blunted flow-dependent CD responses caused by adenosine and transient coronary artery occlusions after L-NAME administration. ACh-induced CD increases resistant to L-NAME and indomethacin were reduced after the administration of intracoronary quinacrine, an inhibitor of phospholipase A2, or proadifen, an inhibitor of cytochrome P-450. Quinacrine or proadifen alone (without L-NAME) did not alter CD responses to ACh, but L-NAME given after proadifen blunted ACh-induced increases in CD. The increases in CD caused by arachidonic acid given after L-NAME + indomethacin were antagonized by proadifen but not altered by quinacrine. Thus, a cytochrome P-450 metabolite of arachidonic acid accounts for L-NAME-resistant and indomethacin-resistant dilation of large epicardial coronary arteries to ACh. Conversely, NO formation is the dominant mechanism of ACh-induced dilation after blockade of the cytochrome P-450 pathway.

A minK-HERG complex regulates the cardiac potassium current I(Kr)

MinK is a widely expressed protein of relative molecular mass approximately 15K that forms potassium channels by aggregation with other membrane proteins. MinK governs ion channel activation, regulation by second messengers, and the function and structure of the ion conduction pathway. Association of minK with a channel protein known as KvLQT1 produces a voltage-gated outward K+ current (I[sK]) resembling the slow cardiac repolarization current (I[Ks]). HERG, a human homologue of the ether-a-go-go gene of the fruitfly Drosophila melanogaster, encodes a protein that produces the rapidly activating cardiac delayed rectifier (I[Kr]). These two potassium currents, I(Ks) and I(Kr), provide the principal repolarizing currents in cardiac myocytes for the termination of action potentials. Although heterologously expressed HERG channels are largely indistinguishable from native cardiac I(Kr), a role for minK in this current is suggested by the diminished I(Kr) in an atrial tumour line subjected to minK antisense suppression. Here we show that HERG and minK form a stable complex, and that this heteromultimerization regulates I(Kr) activity. MinK, through the formation of heteromeric channel complexes, is thus central to the control of the heart rate and rhythm.

Beta 2-adrenergic dilation of resistance coronary vessels involves KATP channels and nitric oxide in conscious dogs

BACKGROUND

We considered that beta 2-adrenergic stimulation may dilate resistance coronary vessels by opening ATP-sensitive potassium (KATP) channels, thereby triggering NO formation.

METHODS AND RESULTS

In conscious instrumented dogs after beta 1-adrenergic blockade, intracoronary (IC) injections of acetylcholine (ACh), nitroglycerin (NTG), and pirbuterol (PIR), a selective beta 2-adrenergic agonist, were performed before and after blockade of NO formation with IC N omega-nitro-L-arginine methyl ester (L-NAME, 50 micrograms.kg-1.min-1 x 12 minutes) or blockade of KATP channels with IC glibenclamide (25 micrograms.kg-1.min-1 x 12 minutes followed by 2 micrograms.kg-1.min-1). PIR (50.0 ng/kg) increased coronary blood flow (CBF) by 32 +/- 6 from 43 +/- 7 mL/min and by only 11 +/- 2 (P < .01) from 40 +/- 7 mL/min after L-NAME. Increases in CBF to ACh were also reduced by L-NAME, but NTG responses were not. Before glibenclamide, PIR increased CBF by 33 +/- 5 from 45 +/- 7 mL/min and by only 14 +/- 3 (P < .01) from 36 +/- 5 mL/min thereafter. CBF responses to ACh and NTG were maintained after glibenclamide. Lemakalim, a selective opener of KATP channels, caused dose-dependent increases in CBF that were partially inhibited by L-NAME. In experiments in which CBF was controlled, the fall in distal coronary pressure caused by PIR was less after L-NAME or glibenclamide than before.

CONCLUSIONS

beta 2-Adrenergic dilation of resistance coronary vessels involves both the opening of KATP channels and NO formation. L-NAME antagonized lemakalim responses consistent with a link between the opening of KATP channels and NO formation in canine resistance coronary vessels.

Immunohistochemical evaluation of the Ca(2+)-binding S-100 proteins S-100A1, S-100A2, S-100A4, S-100A6 and S-100B in salivary gland tumors

The Ca(2+)-binding S-100 proteins are involved in the regulation of a number of cellular processes and an altered expression has been reported in several neoplastic tissues. Tissue specimens of normal salivary glands (n = 23), pleomorphic adenomas (n = 60), basal cell adenomas (n = 6), canalicular ademomas (n = 2), myoepitheliomas (n = 2), adenoid cystic carcinomas (n = 26) and adenocarcinomas NOS (n = 11) were evaluated for the expression of S-100A1, S-100A2, A-100A4, S-100A6 and S-100B by using highly specific polyclonal and monoclonal antibodies generated against the recombinant human protein. In normal salivary glands, the ductal cells showed mild to intense immunoreactivity for S-100A1, S-100A2, S-100A4 and S-100A6, while S-100B was observed in nerve fibers in the connective tissue. The normal myoepithelial cells were unreactive. In pleomorphic adenoma, the luminal tumor cells of the duct-like structures showed moderate to intense immunoreactivity for S-100A2, while reactivity for S-100A1, S-100A4 and S-100A6 was relatively weak. The non-luminal cells, also termed neoplastic myoepithelial cells, showed immunoreactivity for S-100B, while tumor cells in the solid, myxoid and chondroid areas were immunoreactive for S-100A1, S-100A4, S-100A6 and S-100B. The non-luminally located tumor cells in basal cell adenomas and canalicular adenomas, and numerous tumor cells in clusters in myoepitheliomas were intensely reactive for S-100A2. In adenoid cystic carcinomas and in adenocarcinomas not otherwise specified, the luminal cells forming the tubular or cribriform structures were markedly positive for S-100A2 and/or S-100A6. Squamous metaplastic cells in salivary tumors showed intense immunoreactivity for S-100A2. The results of the present study suggest that the majority of the tumor cells in salivary neoplasms, despite the most heterogeneous tumor cell differentiation, express S-100 proteins more heterogeneously than the normal glandular ducts. The salivary ducts in normal glands, the luminal tumor cells and squamous metaplastic cells in the neoplastic lesions were intensely immunoreactive for S-100A2 as compared to S-100A1, S-100A4 or S-100A6. In contrast, the non-luminal tumor cells showed a rather heterogeneous expression of the S-100 proteins.

Beta 2-adrenergic dilation of conductance coronary arteries involves flow-dependent NO formation in conscious dogs

The contribution of nitric oxide (NO) formation to the dilation of large epicardial coronary arteries to beta 1- and beta 2-adrenergic receptor stimulation was investigated in conscious dogs. After beta 1-adrenergic blockade (atenolol, 1.0 mg/kg iv), selective beta 2-adrenergic receptor activation with intracoronary bolus injections of pirbuterol (50 ng/kg) increased coronary blood flow (CBF) by 95 +/- 19% from 48.5 +/- 8.4 ml/min and external epicardial coronary diameter (CD) by 0.14 +/- 0.03 from 3.23 +/- 0.31 mm. After intracoronary N omega-nitro-L-arginine methyl ester (L-NAME, 50 micrograms.kg-1.min-1 x 12 min) was administered, baseline CD decreased but CBF was not altered. After L-NAME, bolus injections of pirbuterol resulted in smaller (P < 0.01) CBF responses (40 +/- 12%), and increases in CD were abolished. When pirbuterol (500 ng.kg-1.min-1) was given as a continuous infusion, CBF increased by 36 +/- 5% from 55.4 +/- 5.8 ml/min and CD by 0.16 +/- 0.03 mm from 3.44 +/- 0.16 mm. L-NAME abolished CD increases and limited (P < 0.01) CBF responses to 9 +/- 3%. When increases in CBF caused by pirbuterol before L-NAME were prevented by arterial constriction, CD increases were suppressed. In contrast, CBF and CD responses to beta 1-adrenergic stimulation were maintained after L-NAME. Thus beta 2-adrenergic dilation of epicardial conductance arteries is primarily a flow-dependent process involving NO formation. In contrast, beta 1-adrenergic activation produces epicardial coronary dilation independent of an L-NAME-sensitive mechanism.

Contrasting effects of blockade of nitric oxide formation on resistance and conductance coronary vessels in conscious dogs

OBJECTIVES

To determine the differential effects of blockade of nitric oxide (NO) formation by an arginine analogue on basal and stimulated NO release in conductance and resistance coronary vessels.

METHODS

In conscious dogs, instrumented for measuring coronary blood flow (CBF) and external epicardial coronary artery diameter (CD), intracoronary (ic) acetylcholine (ACH, 3.0 ng/kg), adenosine (ADENO 100.0 ng/kg) and nitroglycerin (NTG, 10.0 ng/kg) were injected before and after ic N omega-nitro-L-arginine methyl ester (L-NAME, 50.0 micrograms.kg-1 min-1 for 12 min) to block NO synthesis.

RESULTS

Before L-NAME, ACH increased CBF by 65.3 +/- 9.0 from 42.4 +/- 2.9 ml/min and CD by 0.199 +/- 0.035 from 3.374 +/- 0.193 mm. L-NAME failed to alter baseline CBF but reduced (P < 0.01) CD to 3.220 +/- 0.199 mm. CBF responses to ACH were smaller (P < 0.01) (32.8 +/- 5.3 ml/min) after L-NAME. In contrast, ACH-induced increases in CD (0.184 +/- 0.053 mm) were not altered. L-NAME did not change CBF responses to NTG but increased CD responses (0.345 +/- 0.062 vs 0.217 +/- 0.043 mm, P < 0.01). ADENO-induced increases in CBF were smaller after L-NAME (46.5 +/- 5.6 vs 79.8 +/- 10.9 ml/min, P < 0.01). Increases in CD created by ADENO, a flow-dependent phenomenon, were nearly abolished after L-NAME (0.043 +/- 0.018 vs 0.195 +/- 0.026 mm, P < 0.01) and partially restored by ic L-arginine. The effects of L-NAME on CBF and CD responses to ACH and ADENO continuously delivered into the coronary artery were similar to those of boluses.

CONCLUSIONS

L-NAME selectively reduced ACH-induced dilation in resistance coronary vessels but failed to prevent responses of conductance coronary vessels in spite of reducing baseline CD and blocking flow-dependent effects of ADENO. Therefore, blockade of NO formation resulted in disparate effects on receptor-operated dilation of resistance and conductance coronary vessels.

Terfenadine blocks time-dependent Ca2+, Na+, and K+ channels in guinea pig ventricular myocytes

Terfenadine, which blocks delayed rectifier K+ channels (Ik), is structurally related to diphenylalkylamine L-type Ca2+ channel (ICa) blockers and has been reported to render Purkinje fibers inexcitable. We used standard whole-cell patch clamp techniques in isolated guinea pig ventricular myocytes to investigate the direct effect of terfenadine on ICa after discovering that the upstrokes of early afterdepolarizations in guinea pig myocytes were inhibited by the drug at concentrations > or = 10(-6)M. Some data analyzing the effect of terfenadine on time-dependent Na+ channels (INa) and IK also were obtained. All experiments were controlled for time of intracellular dialysis. Terfenadine (3 x 10(-6)M) reduced peak ICa (measured in either K+-containing or Cs+-substituted intracellular solutions from holding potentials of -40 mV) after 10 min exposure [peak at 0 mV in K+-deficient dialysis solution -4.2 +/- 2.3 pA/pF (mean +/- SD, n = 5) versus -13.02 +/- 4.33 pA/pF in control solution (n = 5), p < 0.01], and ICa was almost completely blocked after 15 min drug exposure. Ten minutes of exposure to terfenadine (3 x 10-6M) also caused near-complete blockade of peak INa when INa was measured at -40 mV after 300 ms conditioning pulses from a holding potential of -40 to potentials between -60 and -90 mV. The effect was much less pronounced when INa was measured from a holding potential of -90 mV. After exposure to terfenadine 3 x 10 (-6)M, IK density, measured as peak tail current at -40 mV after 300-ms depolarizations, was also reduced but not eliminated at membrane potentials between -20 and +60 mV. In contrast, exposure to terfenadine caused no significant change in the current-voltage relationship after 300-ms steps from -90 to +60 mV. Terfenadine had no effect on time constants of decay of IK or ICa. These results suggest that terfenadine blocks several time- and voltage-dependent channels, possibly by binding to a common protein structure, not related to ion selectivity, that is primarily associated with time-dependent activation of channel conductance.