Biomedical subjects

K Kitagawa

Publications and source records attributed to K Kitagawa.

At least 37 records · Page 2Linked to original sources

PubMed2001

Selective halogen-magnesium exchange reaction via organomagnesium ate complex.

Halogen-magnesium exchange of various aryl halides is achieved with a magnesium ate complex at low temperatures. Tributylmagnesate (nBu3MgLi) induces facile iodine-magnesium exchange at -78 degrees C. Dibutylisopropylmagnesate (iPr(n)Bu2MgLi) is more reactive than nBu3MgLi, and this reagent accomplishes selective bromine-magnesium exchange at -78 degrees C. This procedure is utilized for the preparation of various polyfunctionalized arylmagnesium species. The exchange of alkenyl halides using this method proceeds with retention of configuration of the double bond.

Journal Article↗

PubMed2001

Developmental changes in Cl(-)-ATPase activity in rat brains.

Developmental changes in brain Cl(-)-ATPase activity were examined using fetal, neonatal and adult rats. The Cl(-)-ATPase activity rapidly increased over 20 postnatal days to a level four-fold higher than that in an 18-day-old fetus. On Western blot analysis using an anti-Cl(-)-ATPase/pump 51 kDa subunit (ClP51) antibody, the amount of ClP51 protein increased in parallel with Cl(-)-ATPase activity. Immunohistochemistry using the same antibody showed Cl(-)-ATPase-like immunoreactivity on the cell membranes of neurons such as cerebral and hippocampal pyramidal cells and cerebellar Purkinje cells, where the immunoreactivity increased with developmental changes in the size and shape of the neurons. These findings suggest that neuronal Cl(-)-ATPase activity markedly increases during early postnatal development with an increase in the amount of Cl(-)-ATPase protein, which may support the formation of inwardly directed neuronal Cl(-) gradients.

Adenosine Triphosphatases↗

PubMed2001

Stoichiometry of subunit e in rat liver mitochondrial H(+)-ATP synthase and membrane topology of its putative Ca(2+)-dependent regulatory region.

Previous studies have revealed that residues 34-65 of subunit e of mitochondrial H(+)-ATP synthase are homologous with the Ca(2+)-dependent tropomysin-binding region for troponin T and have suggested that subunit e could be involved in the Ca(2+)-dependent regulation of H(+)-ATP synthase activity. In this study, we determined the content of subunit e in H(+)-ATP synthase purified from rat liver mitochondria, and we also investigated the membrane topology of a putative Ca(2+)-dependent regulatory region of subunit e using an antibody against peptide corresponding to residues 34-65 of subunit e. Quantitative immunoblot analysis of subunit e in the purified H(+)-ATP synthase revealed that 1 mol of H(+)-ATP synthase contained 2 mol of subunit e. The ATPase activity of mitoplasts, in which the C-side of F(0) is present on the outer surface of the inner membrane, was significantly stimulated by the addition of the antibody, while the ATPase activity of submitochondrial particles and purified H(+)-ATP synthase was not stimulated. The antibody bound to mitoplasts but not to submitochondrial particles. These results suggest that the putative Ca(2+)-dependent regulatory region of subunit e is exposed on the surface of the C-side of F(0) and that subunit e is involved in the regulation of mitochondrial H(+)-ATP synthase activity probably via its putative Ca(2+)-dependent regulatory region.

Animals↗

PubMed2001

Cl(-)-ATPase in rat brain and kidney.

Cl(-)-stimulated ATPase/ATP-dependent Cl(-) pump (Cl(-)-ATPase/pump) has been found as a candidate for an active outwardly directed Cl(-) transporter in brain neurons. (1) A 520-kDa protein complex with Cl(-)-ATPase/pump activity was isolated from rat brain. It consisted of four protein subunits (51, 55, 60, and 62 kDa proteins), the 51-kDa protein being a covalent phosphorylenzyme subunit. (2) An antiserum against the 51-kDa protein inhibited Cl(-)-ATPase/pump activity. Western blot analysis showed an immunoreactive 51-kDa protein in the brain, spinal cord, and kidney. By enzyme histochemistry and immunohistochemistry, Cl(-)-ATPase-like activity or immunoreactivity was observed on the plasma membranes of brain neurons, and on the baso-lateral membranes of type A intercalated cells of renal collecting ducts. (3) Reconstituted Cl(-)-ATPase/pump activity was highest in liposomes with phosphatidylinositol-4-monophosphate. LiCl, an inhibitor of inositolphosphatase, reduced Cl(-)-ATPase activity and increased intracellular Cl(-) concentrations in cultured rat hippocampal neurons with increased phosphatidylinositol turnover. (4) In the brains of patients with Alzheimer's disease (AD), where phosphatidylinositol 4-kinase activity is reduced, Cl(-)-ATPase activity was also reduced. Thus, Cl(-)-ATPase is likely an outwardly directed ATP-dependent Cl(-) transporter that consists of four subunits and is regulated by phosphatidylinositol-4-monophosphate. Changes in Cl(-)-ATPase activity may be related to the pathophysiology of human neurodegenerative diseases. J. Exp. Zool. 289:224-231, 2001.

Adenosine Triphosphatases↗

PubMed2001

CYP2A6*6, a novel polymorphism in cytochrome p450 2A6, has a single amino acid substitution (R128Q) that inactivates enzymatic activity.

By using the polymerase chain reaction technique combined with restriction enzyme fragment length polymorphism (PCR-RFLP), a novel polymorphism of CYP2A6, CYP2A6*6, was detected in 0.4% of the Japanese population. To study the enzymatic properties of the CYP2A6.6 protein with a single amino acid substitution of arginine 128 to glutamine, both this isozyme and the CYP2A6.1 protein (wild-type) were produced in insect cells using a baculovirus system. Coumarin 7-hydroxylation, which reflects CYP2A6 activity, was significantly reduced (one-eighth of normal) in cell lysate from CYP2A6*6-transfected Sf9 cells compared with that lysate from CYP2A6*1-transfected cells. To clarify the mechanism of inactivation of the CYP2A6.6 enzyme, the heme content and reduced CO difference spectrum were examined. Although CYP2A6.6 retained about one-half the heme content of CYP2A6.1, the reduced CO-bound Soret peak was completely lost. These results suggest that the inactivation of CYP2A6.6 is mainly due to disordering of the holoprotein structure rather than a failure of heme incorporation.

Amino Acid Sequence↗

PubMed2001

Facile solid-phase synthesis of sulfated tyrosine-containing peptides: total synthesis of human big gastrin-II and cholecystokinin (CCK)-39.

Chemical synthesis of tyrosine O-sulfated peptides is still a laborious task for peptide chemists because of the intrinsic acid-lability of the sulfate moiety. An efficient cleavage/deprotection procedure without loss of the sulfate is the critical difficulty remaining to be solved for fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase synthesis of sulfated peptides. To overcome the difficulty, TFA-mediated solvolysis rates of a tyrosine O-sulfate [Tyr(SO3H)] residue and two protecting groups, tBu for the hydroxyl group of Ser and 2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf) for the guanidino group of Arg, were examined in detail. The desulfation obeyed first-order kinetics with a large entropy (59.6 J.K-1.mol-1) and enthalpy (110.5 kJ.mol-1) of activation. These values substantiated that the desulfation rate of the rigidly solvated Tyr(SO3H) residue was strongly temperature-dependent. By contrast, the SN1-type deprotections were less temperature-dependent and proceeded smoothly in TFA of a high ionizing power. Based on the large rate difference between the desulfation and the SN1-type deprotections in cold TFA, an efficient deprotection protocol for the sulfated peptides was developed. Our synthetic strategy for Tyr(SO3H)-containing peptides with this effective deprotection protocol is as follows: (i) a sulfated peptide chain is directly constructed on 2-chlorotrityl resin with Fmoc-based solid-phase chemistry using Fmoc-Tyr(SO3Na)-OH as a building block; (ii) the protected peptide-resin is treated with 90% aqueous TFA at 0 degree C for an appropriate period of time for the cleavage and deprotection. Human cholecystokinin (CCK)-12, mini gastrin-II (14 residues), and little gastrin-II (17 residues) were synthesized with this method in 26-38% yields without any difficulties. This method was further applied to the stepwise synthesis of human big gastrin-II (34 residues), CCK-33 and -39. Despite the prolonged acid treatment (15-18 h at 0 degree C), the ratios of the desulfated peptides were less than 15%, and the pure sulfated peptides were obtained in around 10% yields.

Amino Acid Sequence↗

PubMed2001

Aqueous flare elevation induced by transcorneal application of highly selective agonists for prostaglandin E2 receptor subtypes in pigmented rabbits: effect of tetramethylpyrazine.

We examined the disruptive effect of highly selective agonists for prostaglandin E2 receptor subtypes (EP1, EP2, EP3 and EP4) on the blood-aqueous barrier, and evaluated the inhibitory effect of tetramethylpyrazine, an active component of Ligusticum wallichii, on the elevation of aqueous flare induced by the EP agonists in pigmented rabbits. Highly selective EP agonists (ONO-DI-004, EP1 agonist; ONO-AE1-259-01, EP2 agonist; ONO-AE-248, EP3 agonist; ONO-AE1-329, EP4 agonist) at 12.5 to 250 microg/ml were transcorneally administered to the eyes of pigmented rabbits using a glass cylinder. Animals were pretreated intravenously with tetramethylpyrazine (10 or 30 mg/kg) 30 minutes before application of the EP2 or the EP4 agonist. Aqueous flare was measured using a laser flare-cell meter. Aqueous flare intensity was expressed as the area under the curve (AUC) in arbitrary units. After administration of ONO-AE1-259-01 or ONO-AE1-329, aqueous flare increased and then gradually decreased. ONO-DI-004 and ONO-AE-248 had almost no effect on aqueous flare elevation. The AUC of eyes in rabbits pretreated with tetramethylpyrazine, 10 or 30 mg/kg i.v., was significantly smaller than that of eyes in rabbits treated with ONO-AEI-259-01 alone. The AUC of eyes in rabbits pretreated with tetramethylpyrazine, 10 or 30 mg/kg i.v., was not significantly smaller than that of eyes in rabbits treated with ONO-AEI-329 only. The results indicated that EP2 and EP4 agonists induced aqueous flare elevation in pigmented rabbits, and that tetramethylpyrazine inhibited the aqueous flare elevation induced by the EP2 agonist but did not suppress the elevation induced by the EP4 agonist.

Animals↗

PubMed2001

Design and synthesis of new orally active inhibitors of human neutrophil elastase.

To identify new orally active inhibitors, further modification of 1 (ONO-6818) was performed. Peptidic derivatives 4b, 4c and 4n showed more potent inhibitory activity than nonpeptidic derivatives 3a-c. As a result, a series of peptidic inhibitors, 4a-s and 5a-v, were discovered. Among these N-aryl derivatives 5a-g, 5i, 5m and 5o-v showed oral activity. Their oral activity showed good correlation with their metabolic stability. Compounds 5h and 5j-l, which were extremely metabolically unstable in hamster plasma, did not show oral activity. Oral activity was considered to be determined by a combination of at least two factors: oral absorption and metabolic stability.

Administration, Oral↗

PubMed2001

Evolutionary conservation between budding yeast and human kinetochores.

Accurate chromosome segregation during mitosis requires the correct assembly of kinetochores--complexes of centromeric DNA and proteins that link chromosomes to spindle microtubules. Studies on the kinetochore of the budding yeast Saccharomyces cerevisiae have revealed functionally novel components of the kinetochore and its regulatory complexes, some of which are highly conserved in humans.

Chromosome Segregation↗

PubMed2001

Amyloid beta proteins inhibit Cl(-)-ATPase activity in cultured rat hippocampal neurons.

Cl(-)-ATPase in the CNS is a candidate for an outwardly directed neuronal Cl(-) transporter requiring phosphatidylinositol-4-phosphate (PI4P) for its optimal activity. To test its pathophysiological changes in a phosphatidylinositol (PI) metabolism disorder, the effects of neurotoxic factors in Alzheimer's disease (AD), amyloid beta proteins (Abetas), on the Cl(-)-ATPase activity were examined using primary cultured rat hippocampal neurons. Amyloid beta proteins (1-40, 1-42 and 25-35) concentration-dependently (1-100 nM) and time-dependently (from 1 h to 6 day) decreased Cl(-)-ATPase activity and elevated intracellular Cl(-) concentrations ([Cl(-)]i), Abeta25-35 being the most potent. Addition of inositol or 8-Br-cyclic GMP completely reversed these Abeta-induced changes. The recoveries in enzyme activity were attenuated by an inhibitor of PI 4-kinase, 10 microM wortmannin or 20 microM quercetin, but not by a PI 3-kinase inhibitor, 50 nM wortmannin or 10 microM LY294002. The PI, PIP and PIP2 levels of the plasma membrane-rich fraction were lower in the Abeta-treated cells as compared with each control. In the Abeta-exposed culture, but not in control, stimulation by 10 microM glutamate for 10 min significantly increased fragmentation of DNA and decreased cell viability. Addition of inositol or 8-Br-cyclic GMP prevented the effect of Abeta-treatment on the neurotoxicity of glutamate. Thus, Abetas reduce neuronal Cl(-)-ATPase activity, resulting in an increase in [Cl(-)]i probably by lowering PI4P levels, and this may reflect a pre-apoptotic condition in early pathophysiological profiles of AD.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2001

Induction of the HSP110/105 family in the rat hippocampus in cerebral ischemia and ischemic tolerance.

Recently, the authors isolated a novel gene of the HSP110 family, ischemia responsive protein 94 kDa (irp94), and demonstrated the expression of this gene after transient forebrain ischemia. In the current study, the authors investigated the expression profiles of all HSP110 family members including hsp110/105 and osp94/apg-1, after transient forebrain ischemia using rat four-vessel occlusion model. Among three members of the HSP110 family, induction of hsp110/105 was the most prominent after ischemia. hsp110/105 mRNA expression was clearly enhanced from 4 to 24 hours after a 6-minute or longer ischemic period. First, hsp110/105 mRNA expression was induced in the dentate gyrus, and later in the pyramidal layer. HSP110/105 protein expression also was enhanced by a 6-minute or longer period of ischemia. Profiles of HSP110/105 expression after ischemia were similar to those of inducible HSP70. After transient forebrain ischemia for 10 minutes, HSP110/105 protein was induced in the dentate gyrus and the CA3 pyramidal layer, but not in the CA1 pyramidal neurons. However, 6 minutes of ischemia induced the HSP110/105 protein, as well as the HSP70 protein, in the CA1 region. CA1 pyramidal neurons expressing HSP110/105 acquired tolerance against subsequent severe ischemia. In conclusion, HSP110/105 showed the most prominent induction after ischemia among the three HSP110 gene family members. Colocalization of HSP110/105 and HSP70 in the CA1 neurons that acquired tolerance suggested that induced HSP110/105 might contribute to ischemic tolerance together with HSP70.

Animals↗

PubMed2001

Delayed, but marked, expression of apolipoprotein E is involved in tissue clearance after cerebral infarction.

Clearance of infarct tissue would be an important process for tissue repair after a stroke. Delayed clearance may hamper reconstitution of the blood-brain barrier and glial boundary formation. Recent growing evidence has indicated that apolipoprotein E (APOE), a major apoprotein, plays an important role in lipid transport and homeostasis in the brain. The tissue in the infarction contains abundant lipids must be removed for tissue clearance. In the current study, the authors investigated APOE expression after focal ischemia and the functional role of APOE in tissue clearance using APOE-knockout mice. Expression of APOE was delayed, but marked, in immunohistochemistry and immunoblotting 7 days after permanent focal ischemia. Macrophages were found to express APOE in the infarct center. Infarct size was similar after focal ischemia between wild-type and APOE-knockout mice, although there was no APOE protein expression in knockout mice. However, clearance of infarct tissue 2 weeks after ischemia was significantly delayed in APOE-knockout mice compared with wild-type mice. The current study supports current thinking that APOE is a key molecule for tissue remodeling in the brain. Clearance of damaged tissue may be one of the important functions of APOE in the brain.

Animals↗

PubMed2001

Transient crossed cerebellar diaschisis following thalamic hemorrhage.

This report concerns a 65-year-old right-handed woman with cerebral hemorrhage who presented with mild right-sided hemiparesis. Computed tomography (CT) revealed hematoma in the left thalamus and compression of the posterior limb of the internal capsule by a brain edema surrounding the lesion. 99mTc-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) images obtained 4 days after onset showed hypoperfusion in the left thalamus containing a hematoma as well as contralateral cerebellar hypoperfusion to the supratentorial lesion, which is well recognized as crossed cerebellar diaschisis (CCD) after stroke. CT 14 days after the onset revealed reduction of the brain edema of the posterior limb of the internal capsule accompanied by gradual neurological improvement. SPECT obtained 14 and 28 days later showed that CCD had disappeared. In this case report, the authors discuss the disappearance of CCD due to transient edematous compression of the internal capsule following thalamic hemorrhage on serial 99mTc-HMPAO SPECT scans. CCD was possibly caused by the lesion confined to the posterior limb of the internal capsule, which anatomically constitutes the cerebropontocerebellar pathway.

Aged↗

PubMed2001

Significance of earlier carotid atherosclerosis for stroke subtypes.

BACKGROUND AND PURPOSE: In addition to advanced stenosis, earlier stages of carotid atherosclerosis are associated with the risk for stroke. However, the significance has not been established for specific stroke subtypes. This study examines the association of earlier carotid atherosclerosis with stroke subtypes. METHODS: The subjects comprised 1059 patients (mean+/-SD age, 62+/-11 years) with <60% carotid stenosis. With the use of ultrasound, carotid atherosclerosis was evaluated by the plaque score, as defined by the sum of all plaque heights in bilateral carotid arteries. On the basis of neurological signs and symptoms, medical history, and brain MRI, we diagnosed stroke and its subtypes as follows: no stroke (n=738), atherothrombotic infarction (AI) (n=56), lacunar infarction (LI) (n=117), cardioembolic infarction (n=65), cerebral hemorrhage (n=26), and other or unclassified stroke (n=57). RESULTS: The plaque score was higher in AI (10.5+/-5.9) and LI (6.0+/-5.1) groups than in the no-stroke group (4.3+/-4.9) (both P<0.05), although it was similar between other stroke groups and the no-stroke group. Each 1 SD greater plaque score was associated with 2.5-fold (95% CI, 2.0 to 3.2) higher risk for AI and 1.4-fold (95% CI, 1.2 to 1.7) higher risk for LI compared with the no-stroke group. When we adjusted for cardiovascular risk factors, plaque score remained significantly associated with AI but not with LI. By receiver operating characteristic curve analyses, the receiver operating characteristic area for AI (0.81 to 0.86) was greater than that for LI (0.62 to 0.67) when we used plaque score either alone or in combination with cardiovascular risk factors. CONCLUSIONS: Although evaluation of carotid atherosclerosis may aid in the risk assessment for AI and LI, the benefit appears to be greater for AI.

Aged↗

PubMed2001

Neurogenesis by progenitor cells in the ischemic adult rat hippocampus.

BACKGROUND AND PURPOSE: Recently, there has been great interest in adult neurogenesis. We investigated whether transient forebrain ischemia could influence the proliferation of neuronal progenitor in the subgranular zone (SGZ) of the rat hippocampus and whether aging could influence the neurogenesis after ischemia. METHODS: Male Wistar rats were subjected to 4-vessel occlusion model. We used a bromodeoxyuridine (BrdU) labeling method to identify the postproliferation cells and double-immunostaining with confocal microscopy to determine the cell phenotype. RESULTS: The number of BrdU-positive cells in the SGZ increased approximately 5.7-fold 8 days after ischemia, compared with the control. BrdU-positive cells formed clusters, which suggested that these cells had divided from an original progenitor cell, and expressed Musashi1 (Msi1), a marker of neural stem/progenitor cells. Although astrocytes also expressed Msi1 in the adult brain, Msi1-positive cells that formed clusters in the SGZ did not express glial fibrillary acidic protein, an astrocyte marker. About 70% of all BrdU-positive cells in the SGZ represented the neuronal phenotype 4 weeks after the BrdU injection. Although proliferation of progenitor cells was stimulated in both young and older animals, aging accelerated the reduction in newborn cells after ischemia. CONCLUSIONS: Our results indicate that ischemic stress stimulated the proliferation of neuronal progenitor cells in the SGZ of both young and old rats but resulted in increased neurogenesis only in young animals. Our findings will be important in developing therapeutic intervention to enhance endogenous neurogenesis after brain injury.

Aging↗

PubMed2001

GH, GH receptor, GH secretagogue receptor, and ghrelin expression in human T cells, B cells, and neutrophils.

We examined GH and GH receptor expression in human leukemic cell lines and leukocytes of normal subjects to elucidate the cell types expressing GH and GH receptor, the individual variations of their expressions, their correlation and the relationships with serum IgG and IGF-I concentrations. In addition, the expression of GH secretagogue receptor, which enhances GH secretion from the anterior pituitary by synthetic GH secretagogues and that of its endogenous ligand, ghrelin, were also examined in these immune cells. GH expression in human leukemic cell lines was observed mainly in B cell lines at both the mRNA and protein level [3.8 +/- 0.2 pg/10(6) cells in Raji and 19.9 +/- 3.3 pg/10(6) cells in Daudi vs. negligible in T cell lines (Jurkat and Hut-78) and in myeloid cell lines (K-562 and HL-60)]. B cells in normal subjects were also found to be the major immune cells expressing GH mRNA, with significant individual variation. GH receptor mRNA expression was detectable in all human leukemic cell lines, although the expression level varied widely among the cell lines and was weaker than that in the liver. On the other hand, GH receptor mRNA expression was mainly found in B cells, with marked individual variation in normal subjects. There was a positive correlation between the mRNA expressions of GH and GH receptor in B cells of normal subjects (r = 0.89; P < 0.001). Single cell RT-PCR revealed that some B cells expressed both GH and GH receptor transcripts, and others expressed only GH. GH/GH receptor expression levels in B cells did not show any correlation with serum IgG and IGF-I levels in normal subjects. Expression of GH secretagogue receptor and ghrelin was detectable in all immune cells regardless of the maturity and cell types with great individual variations. In summary, GH secreted from B cells may act locally on their own receptors, and their variable expressions may be related to individual immune functions. Widespread distribution of ghrelin and GH secretagogue receptor in human immune cells may indicate unknown biological functions other than enhancing GH secretion in the immune system.

B-Lymphocytes↗

PubMed2001

Facile solid-phase synthesis of sulfated tyrosine-containing peptides: Part II. Total synthesis of human big gastrin-II and its C-terminal glycine-extended peptide (G34-Gly sulfate) by the solid-phase segment condensation approach.

Application of the fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase segment condensation approach to the preparation of sulfated peptides was investigated through the synthesis of human big gastrin-II, a 34-residue sulfated tyrosine [Tyr(SO3H)]-containing peptide. Highly acid-sensitive 2-chlorotrityl resin (Clt resin) was exclusively employed as an anchor-resin for the preparation of the three peptide segments having the C-terminal Pro residue as well as of the Tyr(SO3H)-containing resin-bound segment. By using the PyBOP-mediated coupling protocol [PyBOP=benzotriazolyloxytris(pyrrolidino)phosphonium hexafluorophosphatel, we successively condensed each segment and constructed the 34-residue peptide-resin without any difficulty. The final acid treatment of the fully protected peptide-resin at low temperature (90% aqueous TFA, 0 degree C for 8 h), which can detach a Tyr(SO3H)-containing peptide from the resin and remove the protecting groups concurrently with minimum deterioration of the sulfate, afforded a crude sulfated peptide. After one-step HPLC purification, a highly homogeneous human big gastrin-II was easily obtained in 14% yield from the protected peptide-resin. The sulfate form of the C-terminal glycine-extended gastrin (G34-Gly sulfate), a posttranslational processing intermediate of gastrin-II, was also successfully prepared with the segment condensation approach (11% yield). These results demonstrated the usefulness of the segment condensation protocol for preparing large Tyr(SO3H)-containing peptides.

Gastrins↗

PubMed2001

Roles of mast cells and histamine in mosquito bite-induced allergic itch-associated responses in mice.

We investigated itch-associated responses (scratching) to mosquito bites and the role of histamine and mast cells in mosquito-induced itching in mice. Although the first bites of mosquito Aedes albopictus did not increase scratching, repeated bites increased scratching. The response was not diminished even after an interval of 2 months. Similarly, repeated intradermal (i.d.) injections of salivary gland extract (SGE) from Aedes albopictus increased scratching after SGE injection itself and mosquito bites. The scratching peaked within 10 min and almost subsided by 60 min. The opioid antagonist naloxone (1 mg/kg, s.c.) inhibited scratching following SGE injection. Although the non-sedative H1-histamine-receptor antagonist terfenadine (30 mg/kg, p.o.) significantly suppressed scratching induced by histamine (100 nmol/site, i.d.) in either naive or mosquito-sensitized mice, it did not affect mosquito-induced scratching in mosquito-sensitized mice. Repeated injections of SGE increased scratching in mast cell-deficient (WBB6F1-W/Wv) mice as well as in normal (WBB6F1-+/+) littermates. Repeated exposure to mosquito bites roughly doubled serum concentrations of total IgE and IgG1, but not IgG2a. Repeated injections of SGE markedly increased plasma extravasation induced by mosquito bites and such an increase was almost completely suppressed by terfenadine (30 mg/kg, p.o.). The results show the presence of histamine-mediated and histamine-independent mechanisms in cutaneous itching and suggest that histamine probably released from mast cells does not play an important role in itching in immediate allergic reaction. Our murine model of mosquito itching may be useful for studying the mechanisms of immediate allergic itching.

Aedes↗