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X L Zheng

Publications and source records attributed to X L Zheng.

At least 19 recordsLinked to original sources
PubMed2006

Increased ADAMTS-13 proteolytic activity in rat hepatic stellate cells upon activation in vitro and in vivo.

INTRODUCTION: ADAMTS-13 is a member of A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS) family, primarily synthesized in hepatic stellate cells (HSCs), one of the major cell types transdifferentiating into myofibroblasts during liver fibrosis. However, the association between ADAMTS-13 expression and HSC activation or liver fibrosis is not known. METHODS: In this study, we determined the ADAMTS-13 mRNA, protein, and activity in isolated primary HSCs upon activation on a plastic dish and in liver after administration of carbon tetrachloride (CCl(4)) in rats. RESULTS: We showed that ADAMTS-13 antigen and proteolytic activity in the activated rat HSCs were dramatically increased, whereas ADAMTS-13 mRNA in these cells was only minimally altered. Similarly, the ADAMTS-13 antigen and proteolytic activity in rat liver after CCl(4) injury were also significantly increased, whereas the ADAMTS-13 mRNAs in these liver tissues were only slightly increased compared with normal. Surprisingly, despite the dramatic up-regulation of ADAMTS-13 protein synthesis in the activated HSCs after CCl(4) administration, the plasma levels of ADAMTS-13 protease in rats did not increase concordantly. CONCLUSION: We conclude that the up-regulation of ADAMTS-13 protein expression in rat HSCs during activation in vitro and in vivo suggests the possibility of ADAMTS-13 proteolysis, an important part of function of the activated HSCs, perhaps through modulation of liver regeneration or formation of liver fibrosis after various injuries. The data also suggest the minimal contribution of the activated HSCs in regulation of plasma levels of ADAMTS-13 protease.

ADAM Proteins↗
PubMed2006

Inhibitory autoantibodies against ADAMTS-13 in patients with thrombotic thrombocytopenic purpura bind ADAMTS-13 protease and may accelerate its clearance in vivo.

BACKGROUND: Many patients with acquired thrombotic thrombocytopenic purpura (TTP) harbor autoantibodies that may bind and/or inhibit ADAMTS-13 proteolytic activity and accelerate its clearance in vivo. METHODS: To test this hypothesis, we determined ADAMTS-13 activity and antigen levels in parallel plasma samples from patients clinically diagnosed with TTP. Collagen binding, GST-VWF73 and FRETS-VWF73 assays were used to determine ADAMTS-13 activity and to detect inhibitory autoantibodies. Enzyme-linked immunosorbent assay (ELISA) and immunoprecipitation plus Western blotting (IP/WB) were used to detect total anti-ADAMTS-13 IgG (inhibitory and non-inhibitory). RESULTS: Among 40 patients with TTP (21 idiopathic and 19 non-idiopathic), inhibitory autoantibodies were detected (by FRETS-VWF73) in 52% of idiopathic and 0% of non-idiopathic TTP patients. In contrast, non-inhibitory IgG autoantibodies were detected in 29% of idiopathic and 50% of non-idiopathic TTP patients. The concentration of inhibitory IgG autoantibody in idiopathic TTP patients was significantly higher than that of non-inhibitory IgG in either idiopathic or non-idiopathic TTP patients. Idiopathic TTP patients demonstrated significantly reduced ADAMTS-13 activity compared with non-idiopathic patients, but only slightly lower ADAMTS-13 antigen levels. Interestingly, patients with inhibitory autoantibodies exhibited significantly lower ADAMTS-13 antigen levels than those with only non-inhibitory IgG autoantibodies or no autoantibody. Serial plasma exchanges increased levels of ADAMTS-13 activity and antigen concurrently in patients with inhibitory autoantibodies. CONCLUSION: The identification of severe ADAMTS-13 deficiency and autoantibodies or inhibitors appears to be assay-dependent; the inhibitory IgG autoantibodies, in addition to binding and inhibiting ADAMTS-13 proteolytic activity, may accelerate ADAMTS-13 clearance in vivo.

ADAM Proteins↗
PubMed2006

Characterization and stability investigation of cu,zn-superoxide dismutase covalently modified by low molecular weight heparin.

Cu,Zn-superoxide dismutase (SOD) was chemically modified with low molecular weight heparin (LMWH). To characterize the conjugate, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (native PAGE) with protein staining and polysaccharide staining were employed. The stabilities of the modified enzyme to heat, acid, alkali, and trypsin treatment were also investigated. SDS-PAGE of the conjugate presented two major bands, and native PAGE of the conjugate showed similar banding position with protein staining and polysaccharide staining, which was different from that of the unmodified SOD and LMWH/SOD mixture. Moreover, the conjugate migrated faster with increasing extent of the modification. Enhanced heat stability, acid resistance, alkali resistance, and anti-trypsin stability of the modified enzyme were observed compared with those of the unmodified enzyme. Results of the study suggest that covalent linkage in LMWH-SOD can be effectively characterized by electrophoretic techniques and the chemical modification of SOD with LMWH can enhance the stabilities of the enzyme. In addition, native PAGE with protein staining can be used to evaluate the extent of the modification.

Animals↗
PubMed2005

Thermochemical and kinetic analyses on oxidation of isobutenyl radical and 2-hydroperoxymethyl-2-propenyl radical.

In recognition of the importance of the isobutene oxidation reaction in the preignition chemistry associated with engine knock, the thermochemistry, chemical reaction pathways, and reaction kinetics of the isobutenyl radical oxidation at low to intermediate temperature range were computationally studied, focusing on both the first and the second O2 addition to the isobutenyl radical. The geometries of reactants, important intermediates, transition states, and products in the isobutenyl radical oxidation system were optimized at the B3LYP/6-311G(d,p) and MP2(full)/6-31G(d) levels, and the thermochemical properties were determined on the basis of ab initio, density functional theory, and statistical mechanics. Enthalpies of formation for several important intermediates were calculated using isodesmic reactions at the DFT and the CBS-QB3 levels. The kinetic analysis of the first O2 addition to the isobutenyl radical was performed using enthalpies at the CBS-QB3 and G3(MP2) levels. The reaction forms a chemically activated isobutenyl peroxy adduct which can be stabilized, dissociate back to reactants, cyclize to cyclic peroxide-alkyl radicals, and isomerize to the 2-hydroperoxymethyl-2-propenyl radical that further undergoes another O2 addition. The reaction channels for isomerization and cyclization and further dissociation on this second O2 addition were analyzed using enthalpies at the DFT level with energy corrections based on similar reaction channels for the first O2 addition. The high-pressure limit rate constants for each reaction channel were determined as functions of temperature by the canonical transition state theory for further kinetic model development.

Journal Article↗
PubMed2001

Epidermal growth factor induction of apolipoprotein A-I is mediated by the Ras-MAP kinase cascade and Sp1.

Insulin induces apolipoprotein A-I, apoA-I gene transcription via a membrane receptor with intrinsic tyrosine kinase activity. This finding prompted us to ask whether the gene is stimulated by epidermal growth factor (EGF), EGF a peptide hormone that binds to another member of the receptor superfamily with tyrosine kinase activity. Our data showed that like insulin, EGF increased abundance of apoA-I protein and transcription of the gene in human hepatoma, Hep G2 cells. The effects of both hormones appeared direct because their induction of apoA-I gene transcription was not affected by the protein synthesis inhibitor, cycloheximide. Although both insulin and EGF stimulate apoA-I expression, each hormone binds to a distinct membrane receptor thus suggesting differential intracellular signaling. Therefore, we used a panel of inhibitors to define the pathway(s) that mediate the actions of these hormones. Whereas, the actions of EGF required only the Ras-mitogen-activated protein, MAP kinase, those of insulin were mediated by equal participation of both the Ras-MAP kinase and protein kinase C, PKC cascades. Despite differences in signaling pathways triggered by each hormone receptor, the activation of apoA-I transcription required the participation of a single transcription factor, Sp1. Furthermore, EGF induction of transcription was attenuated by mutating the MAP kinase site at amino acid, Thr(266) rendering Sp1 phosphorylation deficient. In summary, EGF stimulation of apoA-I expression is mediated solely by the Ras-MAP kinase cascade and enhanced activity of this pathway requires Sp1 with an intact phosphorylation site at Thr(266). However, insulin induction of this gene is different and requires both Ras-MAP kinase and PKC pathways but their actions are also mediated by Sp1.

Amino Acid Sequence↗
PubMed2001

Study on second harmonic generation of 10-hydrocarbylacridones.

Values of second-order polarizabilities (beta(xxx)), the composite magnitude (beta(CT microg)) of molecular hypersusceptibilities and the second harmonic generation (SHG) of microcrystal were used to characterize and evaluate the second-order nonlinear optical performance of 10-hydrocarbylacridones. Using Nd:YAG as a laser source, the SHG values of these compounds in powder as compared with urea powder were obtained, compared with the calculated values of beta(CT microg) and beta(xxx) found by solvatochromic method. The results showed that the SHG values of compounds 1, 2, and 5 are larger than that of urea. Compound 5 has a highest beta(CT microg) value among the 12 compounds. Although the different electronegativities of hydrocarbyl (R) attached to nitrogen atom should have an effect on the extent of intralmolecular charge-transfer and further influence SHG, beta(CT microg) or beta(xxx) values, the relationships between electronegativity of R and SHG, beta(CT microg) or beta(xxx) could not be found. But it is found that the bigger the donating-electron ability of R, the longer the maximum absorption wavelength of 10-hydrocarbylacridone molecules.

Acridines↗
PubMed2001

Study on second harmonic generation of 9-benzylidene-substituted-10-methyl-9,10-dihydroacridines.

Eight 9-benzylidene-substituted-10-methyl-9,10-dihydroacridine derivatives were synthesized from acridine as starting material and were characterized by 1H-NMR, 13C-NMR, Ms and elemental analysis. The second harmonic generation (SHG) values of these compounds were determined in powder using Nd:YAG as a laser source, as compared with urea powder, and the values of second-order polarizabilities (betaxxx), the values of the composite magnitude (betaCTmicrog) of molecular hypersusceptibilities and their moment of these compounds were obtained by the solvatochromic method under ground state for everyone. The results showed that SHG value of 10 is higher than that of urea; the betaCTmicrog of 5 (107.8 x 10(-30) esu) is lower than that of 4-nitro-N,N-dimethylaniline (30 x 10(-30) esu); the betaCTmicrog of 7 (350.8 x 10(-30) esu) and 10 (244.6 x 10(-30) esu) are higher than that of 4-nitro-N,N-dimethylaniline; the betaCTmicrog of 8 (3553 x 10(-30) esu), 11 (1187 x 10(-30) esu) and 12 (1163 x 10(-30) esu) are much more higher than that of 4-nitro-N,N-dimethylaniline. The results demonstrated that this series of compounds possesses good second-order nonlinear optical (NLO) property. The regular relationship could not be obtained between electronegativity of substituents (R) attached to benzylidene ring and SHG values or betaCTmicrog values although the Rs are different in electronegativity and should make an effect on the extent of intramolecular electron-transfer and would consequently influence SHG or betaCTmicrog. The electron-withdrawing ability of R from benzylidene ring played an important role on lambdamax of these compounds.

Acridines↗
PubMed2000

Activation of apolipoprotein AI gene expression by protein kinase A and kinase C through transcription factor, Sp1.

Our previous finding that insulin induces apolipoprotein AI (apoAI) transcription points to the participation of intracellular signaling. This finding prompted us to ask whether two classical G-protein-coupled signaling pathways requiring activated protein kinase A (PKA) or kinase C (PKC) may also regulate apoAI. Therefore, human hepatoma, Hep G2 cells stably transfected with pAI.474-CAT, a reporter construct spanning -474 to -7 of apoAI DNA fused to chloramphenicol acetyltransferase (CAT) were treated with 10 microm forskolin (FSK) or 50 nm phorbol dibutyrate (PDBu) to activate PKA and PKC, respectively. Results showed that the apoAI promoter activity increased 4-5-fold following 24 h of treatment with either FSK or PDBu. Induction by either agent was blocked with actinomycin D but not the protein synthesis inhibitor, cycloheximide. The PKA inhibitor, PKI 14-22 amide, abrogated induction by FSK, 100 microm 8-bromo-cAMP, or 100 ng/ml cholera toxin, but it had no effect on activation via PKC. Similarly, PDBu induction was attenuated by 2 microm of the PKC inhibitor, GF109203X, but it did not affect FSK activity. Next we used deletional constructs to show that the actions of FSK and PDBu required the insulin-responsive core element (IRCE). This motif matched the consensus binding site for the transcription factor, Sp1. The binding of Sp1 to the IRCE was confirmed by gel-retardation and supershift analysis. Site-directed mutagenesis of the IRCE eliminated Sp1 action and induction by FSK or PDBu. Whereas overexpression of Sp1 enhanced basal and FSK or PDBu induced promoter activity, transfection of an antisense oligomer against Sp1 mRNA attenuated both parameters. In summary, activation of PKA or PKC increases apoAI promoter activity. The activity of both signaling pathways is mediated by the IRCE, a motif that binds the transcription factor, Sp1.

Apolipoprotein A-I↗
PubMed2000

Interleukin-1beta, Src- and non-Src tyrosine kinases, and nitric oxide synthase induction in rat aorta in vitro.

We studied the potential roles for endogenous interleukin-1beta (IL-1beta) and for several signaling pathways in the spontaneous induction in vitro of inducible nitric oxide synthase (iNOS) in endothelium-denuded rat aorta rings. Added IL-1beta augmented, whereas the IL-1beta receptor antagonist IL-1ra blocked, spontaneous iNOS induction. Furthermore, increases in IL-1beta mRNA preceded those of iNOS mRNA. Mitogen-activated protein kinase kinase and phosphatidyl inositol 3' kinase inhibition did not block iNOS induction, whereas nuclear factor kappaB inhibition did. The sarcoma virus tyrosine kinase (Src) family-selective inhibitor 4-amino-5(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP1) blocked the upregulation of IL-1beta mRNA and the subsequent induction of iNOS but not the induction of iNOS stimulated by exogenously added IL-1beta. In contrast, the non-Src inhibitors TP 47/AG 213 and genistein and the tyrosine phosphatase inhibitor vanadate did not affect the spontaneous upregulation of IL-1beta mRNA but blocked both the IL-1beta-mediated and spontaneous induction of iNOS. We conclude that 1) the upregulation of tissue IL-1beta, via a signaling pathway involving a Src family kinase, plays a key role in rat vascular iNOS induction and 2) non-Src tyrosine kinases play roles downstream from IL-1beta for iNOS induction.

Animals↗
PubMed2000

[Cloning and sequence analysis of SSU rRNA gene of cutaneous leishmaniasis pathogen from Xinjiang of China].

OBJECTIVE: By sequencing of SSU rRNA gene cloning from Xinjiang cutaneous leishmaniasis pathogen (XJCLP) to provide evidence for identification of the pathogen. METHODS: By PCR assay with primers R222 and R333, the specific fragment had been produced from SSU rRNA gene of XJCLP, L. infantum, L. tropica and cloned into pGEM-T Easy vector. The clones were sequenced by the Sanger dideoxy-mediated chain termination method, analysis of SSU rRNA gene sequences from XJCLP, L. tropica, L. infantum with DNASIS. RESULTS: Sequence analysis showed that the specific fragment of SSU rRNA gene from XJCLP, L. infantum, L. tropica, were all 394 bp in length. There were 391 bases identical and three point mutations between the sequences of XJCLP and L. tropica, the similarity being 99.2%; 390 bases identical and three point mutations and one insertion/deletion between the sequences of XJCLP and L. infantum, the similarity being 99.0%. One insertion/deletion between the sequences of L. tropica and L. infantum, the similarity being 99.7%. The primary and secondary structures of SSU rRNA gene from XJCLP differed from those of L. infantum and L. tropica. A retrieval from GenBank confirmed that these 394 bp sequence are new gene sequences. CONCLUSION: The primary and secondary structures of SSU rRNA gene from XJCLP, L. infantum, L. tropica were different. 394 bp sequence from SSU rRNA gene of XJCLP is a new gene sequence.

Animals↗
PubMed1999

Differential induction of nitric oxide synthase in rat gastric and vascular smooth muscle tissue: distinct tissue distribution and distinctive signaling pathways.

In rat aorta rings (RA) and in gastric circular muscle (CM) and gastric longitudinal muscle (LM) preparations maintained in vitro, inducible nitric oxide synthase (iNOS) induction was monitored functionally (1 mM L-arginine-induced relaxation), biochemically (appearance of iNOS mRNA), and immunohistochemically. Functional iNOS (L-arginine-mediated relaxation) was induced in RA and CM tissues (but NOT in the LM preparation) over 2 to 5 h. iNOS induction was detected by immunocytochemistry in RA smooth muscle elements and in macrophage-like cells in CM. Functional iNOS induction correlated with iNOS mRNA induction. In the RA and CM, functional iNOS induction was blocked by both actinomycin D and cycloheximide; actinomycin D also blocked the appearance of iNOS mRNA in both tissues. In contrast, cycloheximide blocked CM (but not RA) iNOS mRNA induction. In CM tissue, functional iNOS induction was not affected by genistein, tyrphostin 47/AG213, or vanadate. But, in the RA, both genistein and tyrphostin 47/AG213 blocked the appearance of functional iNOS; neither inhibitor prevented the appearance of RA iNOS mRNA. Vanadate, in the RA tissue, blocked both the appearance of iNOS mRNA and the induction of functional iNOS. In RA tissue, but not in the CM, inhibitors of NF-kappaB activation blocked the appearance of both functional iNOS and iNOS mRNA. We conclude that in different smooth muscle preparations (aorta versus gastric), there can be a differential induction of iNOS mRNA and "functional" iNOS not only in different cellular elements but also in terms of different signaling pathways.

Animals↗
PubMed1998

Expression of constitutively activated Gialpha2 in vivo ameliorates streptozotocin-induced diabetes.

Streptozotocin treatment in vivo generates a model of insulin-dependent diabetes mellitus via destruction of the pancreatic beta-cells responsible for insulin secretion. Tissue-specific expression of the Q205L constitutively activated mutant form of the G-protein Gialpha2 in vivo ameliorates streptozotocin-induced insulin-dependent diabetes mellitus in transgenic mice. Conditional expression of Q205L Gialpha2 in vivo in liver, skeletal muscle, and adipose tissue markedly rectifies glucose tolerance, fasting glucose levels, and glycogen synthase activation in the mice with insulin-dependent diabetes mellitus, providing a novel therapeutic target for diabetes.

Adipose Tissue↗
PubMed1998

Parallel contractile signal transduction pathways activated by receptors for thrombin and epidermal growth factor-urogastrone in guinea pig gastric smooth muscle: blockade by inhibitors of mitogen-activated protein kinase-kinase and phosphatidyl inositol 3'-kinase.

Using a guinea pig gastric longitudinal smooth muscle preparation, we have compared the contractile signaling pathways triggered by the thrombin receptor-activating peptide, TFLLR-NH2 (TF) and by epidermal growth factor-urogastrone (EGF). In addition to inhibitors of tyrosine kinase [tyrphostin 47/AG213, genistein and the src-selective inhibitor CP118,556/PP1], cyclooxygenase (indomethacin, INDO) and diacylglycerol lipase (U57, 908), we also used the signal pathway probe inhibitors of mitogen-activated protein-kinase-kinase (MEK:PD98059), phosphatidylinositol 3'-kinase [PI3K: Wortmannin (WM) and LY294002], protein kinase C [PKC: GF109203X (GF)], and of the EGF-receptor kinase (PD153035). We found that in addition to the inhibition of both TF and EGF-stimulated contractions by the inhibitors of tyrosine kinase, cyclooxygenase and diacylglycerol lipase, the actions of TF and EGF were also attenuated by PD98059, WM/LY294002 and GF. However, PD153035 blocked only EGF-triggered contractions. The contractile actions of both TF and EGF were dependent on extracellular calcium. In contrast, the contractile action of arachidonic acid, via a presumed cyclooxygenase product that mediated the contractions caused by both TF and EGF, was not blocked by any of the signal pathway probe inhibitors. The contractile actions of both TF and EGF were accompanied by increases in tissue phosphotyrosyl proteins and an increase in tissue c-src kinase activity. We conclude that protease-activated receptor no. 1- (thrombin receptor) mediated contractions in the logitudial muscle, like EGF receptor-activated responses, require the influx of extracellular calcium and use parallel signal pathways upstream of the cyclooxygenase step, involving MEK, PI3K, kinase C and possibly cellular src. The TF-induced response did not involve trans-activation of the EGF receptor kinase; but the converse (i.e., trans-activation of protease-activated receptor no. 1 (thrombin receptor) by the EGF receptor kinase) could not be ruled out.

Animals↗
PubMed1997

Force measurement on fracture site with external fixation.

A force measurement device has been designed to monitor the mechanical properties of fracture site with external fixation. Forces are measured through electric resistance strain gauges mounted on fixation framework and the measurement results are displayed on an LCD screen. The device features a force range of 0-10 kg with linearity and repeatability less than 1% and accuracy less than 0.1 kg.

Biomechanical Phenomena↗
PubMed1997

Induction of nitric oxide synthase in rat gastric smooth muscle preparations.

The induction in vitro of inducible nitric oxide synthase (iNOS) in intact gastric circular (CM) and longitudinal (LM) smooth muscle preparations was evaluated 1) pharmacologically, by the appearance of 1 mM L-arginine (L-Arg)-induced relaxation in a precontracted tissue; 2) biochemically, according to the appearance of iNOS mRNA using a reverse transcriptase-polymerase chain reaction; and 3) immunohistochemically, using an iNOS-specific antibody. Functionally, iNOS induction affected the contractile properties of the CM but not the LM preparation. The time course of iNOS induction monitored pharmacologically paralleled exactly the appearance of iNOS mRNA. The relaxant response to L-Arg in iNOS-induced CM tissues was blocked by the iNOS inhibitor aminoguanidine and by the guanylyl cyclase inhibitor LY-83583. The addition of oxyhemoglobin to the organ bath also attenuated the relaxant response, but tetrodotoxin had no effect. The transcriptional inhibitor actinomycin D completely blocked iNOS induction as assessed by both pharmacological and biochemical criteria. In iNOS-induced preparations the iNOS immunoreactivity was not detected in the smooth muscle elements but was localized in a layer of macrophage-related cells that were in apposition to the CM smooth muscle elements. We conclude that the spontaneous induction of iNOS in rat gastric tissue can affect the pharmacomechanical reactivity of the CM elements and that this regulation of the CM contractility is due to the induction of iNOS in a set of macrophage-related cells that are closely apposed to the CM elements so that they selectively affect only the contractility of the CM preparation.

Animals↗
PubMed1997

Tyrosine kinase inhibitor-sensitive contractile action of ethanol in gastric smooth muscle: comparison with the action of epidermal growth factor.

We have evaluated the signal transduction pathways whereby, in comparison with epidermal growth factor-urogastrone, ethanol causes a rapid contractile response in guinea pig gastric longitudinal muscle. As for epidermal growth factor (EGF), the ethanol-induced contraction required extracellular calcium, was sensitive to the tyrosine kinase inhibitors genistein and tyrphostin 47 (AG213), and was blocked by both the cyclo-oxygenase inhibitor, indomethacin, and the diacylglycerol lipase inhibitor, U57908. The 50% effective concentration (EC50) for the contractile action of ethanol (approximately 140 mM) was lower than that for propanol and methanol and was not affected by the aldehyde dehydrogenase inhibitor, 4-methyl pyrazole. The actions of ethanol were distinct from those of EGF in that EGF-induced contractions were sensitive to the kinase C inhibitor GF109203X, and the EGF receptor kinase inhibitor PD153035, whereas ethanol-induced contractions were refractory to these inhibitors. Further, EGF-induced contractions were attenuated by the voltage-sensitive calcium channel antagonist, nifedipine, whereas the ethanol-induced contractile response was resistant to nifedipine but blocked by the "receptor-operated" calcium channel antagonist SKF96365. We conclude that ethanol without metabolism via alcohol dehydrogenase causes a contractile response in gastric longitudinal muscle tissue via a tyrosine kinase inhibitor-sensitive signal pathway that is parallel in many respects but yet is distinct from that activated by EGF.

1-Propanol↗
PubMed1997

Contractile action of ethanol in guinea pig gastric smooth muscle: inhibition by tyrosine kinase inhibitors and comparison with the contractile action of epidermal growth factor-urogastrone.

We observed a contractile action of ethanol (20-500 mM) and other alcohols (methanol and propanol, but not butanol) in guinea pig gastric longitudinal (LM) and circular (CM) smooth muscle preparations. The potency order for the alcohols in the LM preparation was: ethanol = propanol > methanol; and in the CM preparation, propanol > ethanol > methanol. Like epidermal growth factor-urogastrone (EGF), the contractile actions of ethanol in the LM and CM preparations required extracellular calcium and were blocked by the tyrosine kinase inhibitors, genistein and tyrphostin-47 (AG213). The tyrosine phosphatase inhibitor, pervanadate, potentiated the contractile action of ethanol in the LM preparation. Ethanol-induced contractions in both preparations were not affected by 4-methyl pyrazole, an inhibitor of alcohol dehydrogenase, and were unaffected by tetrodotoxin, atropine, prazosine or yohimbine. In the LM preparation, like EGF, the contractile action of ethanol was blocked by the cyclooxygenase inhibitor, indomethacin, and the diacylglycerol lipase inhibitor, U57,908; in the CM preparation, contractions caused by ethanol and EGF were still observed in the presence of these two inhibitors. Contractions caused by ethanol and EGF in the LM preparation were not affected by the epoxygenase inhibitor, ketoconazole; the lipoxygenase inhibitor, nordihydroguaiaretic acid; or the phospholipase A2 inhibitor, mepacrine. In contrast, in the LM preparation, EGF-induced contractions were attentuated by the EGF receptor-kinase inhibitor, PD153035; the MAP-kinase-kinase (MEK) inhibitor, PD98059; the kinase C inhibitor, GF109203X; and the phosphatidylinositol 3'-kinase inhibitors, Wortmannin and LY294002; whereas ethanol-induced contractions were unaffected by these inhibitors. Both ethanol and EGF caused small increases in the phosphotyrosyl protein content of the gastric tissue. We conclude that ethanol causes its contractile effects in the distinct gastric LM and CM preparations independent of nerve-released agonists and via a tyrosine kinase inhibitor-sensitive signal pathway that is in many respects similar to, but distinct from the one activated by EGF.

Animals↗