Biomedical subjects

H Saito

Publications and source records attributed to H Saito.

At least 145 records · Page 8Linked to original sources

PubMed2001

Repeated administration of CGP 46381, a gamma-aminobutyric acidB antagonist, and ethosuximide suppresses seizure-associated cyclic adenosine 3'5' monophosphate response element- and activator protein-1 DNA-binding activities in lethargic (lh/lh) mice.

To characterize seizure-associated increases in cerebral cortical and thalamic cyclic AMP responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities in lethargic (lh/lh) mice, a genetic model of absence seizures, we examined the effects of ethosuximide and CGP 46381 on these DNA-binding activities. Repeated administration (twice a day for 5 days) of ethosuximide (200 mg/kg) or CGP 46381 (60 mg/kg) attenuated both seizure behavior and the increased DNA-binding activities, and was more effective than a single administration of these drugs. These treatments did not affect either normal behavior or basal DNA-binding activities in non-epileptic control (+/+) mice. Gel supershift assays revealed that the increased CRE-binding activity was attributable to activation of the binding activity of CREB, and that the c-Fos-c-Jun complex was a component of the increased AP-1 DNA-binding activity.

Animals↗

PubMed2001

Protein-tyrosine kinase Syk expressed in human nasal fibroblasts and its effect on RANTES production.

Fibroblasts, a rich source of chemokines, interact with eosinophils and play a key role in the pathogenesis of airway disease. RANTES is produced by fibroblasts to attract and activate eosinophils. LPS is known to induce RANTES and cause protein tyrosine phosphorylation. Nonreceptor protein tyrosine kinase Syk is widely expressed and an important role in intracellular signal transduction in hemopoietic cells. In the present study, we examined whether Syk was expressed in a number of primary human nasal polyp tissue-derived fibroblast lines and whether it played some role in cellular function. Syk proteins were expressed in human nasal fibroblasts, but the expression level varied. There were positive correlations between the level of Syk expression and RANTES production induced by LPS. Overexpression of wild-type Syk by gene transfer enhanced RANTES production from nasal fibroblasts stimulated with LPS. The decrease of Syk expression by the administration of Syk antisense inhibited RANTES production. These results suggest that Syk expression affects RANTES production in fibroblasts of nasal polyps.

Blotting, Western↗

PubMed2001

Dietary restriction impairs neutrophil exudation by reducing CD11b/CD18 expression and chemokine production.

HYPOTHESIS: Patients with malnutrition are susceptible to infection. Polymorphonuclear neutrophils (PMNs) are the major effector of the nonspecific immune response in host resistance to infection. Dietary restriction may impair PMN-mediated immunity in the peritoneal cavity by reducing PMN exudation, adhesion molecule expression on PMNs, and chemokine production. DESIGN: Randomized study of murine glycogen-induced peritonitis with dietary restriction. SETTING: University research laboratory. MATERIALS: Male C57BL/6J mice. INTERVENTIONS: Mice (N = 204) were assigned to ad libitum, moderate, and severe diet-restricted groups receiving mouse chow ad libitum (132 g/kg, 66 g/kg, and 33 g/kg daily for 7 days, respectively). After dietary restriction with or without 1 day of refeeding, mice were administered glycogen intraperitoneally to induce cell exudation. MAIN OUTCOME MEASURES: CD11b, CD18, and CD62L expressions on circulating PMNs, phagocytosis, and reactive oxygen intermediate production by exudative PMNs were measured after glycogen installation. The levels of PMN-specific chemokine, macrophage inflammatory protein 2 (MIP-2), in peritoneal lavage fluid were also measured. These parameters were measured after glycogen installation in the refeeding experiment. RESULTS: Seven days of dietary restriction decreased CD11b/CD18 expression on circulating PMNs, MIP-2 levels in peritoneal lavage fluid, and subsequent PMN exudation into the peritoneal cavity early in peritonitis. Both CD11b and CD18 expression on circulating PMNs and MIP-2 levels correlated significantly with numbers of exudative PMNs. Seven days of dietary restriction also impaired phagocytosis, while up-regulating reactive oxygen intermediate production by exudative PMNs. Only 1 day of ad libitum refeeding normalized CD11b/CD18 expression with PMN exudation into the peritoneal cavity. CONCLUSIONS: Short-term dietary restriction impairs PMN exudation into local inflammatory sites in murine peritonitis by reducing CD11b/CD18 expression and MIP-2 production. Even brief nutritional replenishment in diet-restricted patients may improve host defense via restoring these PMN functions and chemokine production at local inflammatory sites.

Animals↗

PubMed2001

Novel heterozygous missense mutation in the platelet glycoprotein Ib beta gene associated with isolated giant platelet disorder.

The glycoprotein (GP) Ib/IX/V complex plays an important role in primary hemostasis, serving as the platelet receptor for von Willebrand factor (vWF). Recent studies have shown that the phenotype caused by mutations in the subunits of the GPIb/IX complex spans a wide spectrum; from the normal phenotype, to isolated giant platelet disorders (GPD), and to the full-blown bleeding disorder, the Bernard-Soulier syndrome (BSS). We characterize here a novel missense mutation of the GPIb beta gene associated with isolated GPD. In the patient's platelets, the expression level of the GPIb/IX complex was moderately reduced compared with that of the GPIIb/IIIa complex, whereas the latter was expressed at higher levels than in a normal control. Immunoblot analysis showed normal electrophoretic mobility of GPIb alpha, GPIb beta, and GPIX. However, the amount of GPIb beta was approximately 66% of the normal value. DNA sequencing analysis revealed a novel heterozygous missense mutation in the GPIb beta gene that converts Arg (CGC) to Cys (TGC) at residue 17. Transient transfection studies demonstrated that mutant GPIb beta protein was not detected in transfected 293T cells. These findings indicated that null expression of the abnormal GPIb beta causes decreased expression of the complex and results in the GPD phenotype in the patient, and suggested that homozygosity of the mutation may lead to a BSS phenotype in vivo.

Adult↗

PubMed2001

Interferon regulatory factor 1 promoter polymorphism and response to type 1 interferon.

The clinical success of interferon-treatment has been found to vary in different individuals. To explain this, we hypothesized that responses to type 1 interferons could be partly determined by interferon regulatory factor-1 gene transcription, because the latter is an important transcription factor in the interferon system. We demonstrated that the antiproliferative effect of type 1 interferons on human liver cancer cells correlates with levels of transcription of the interferon regulatory factor-1 gene in parallel with those of p21(WAF-1) expression. Here, we investigated whether mutations in the interferon regulatory factor-1 gene cause different responses to type 1 interferons. DNA from several human liver cancer cell lines and peripheral blood mononuclear cells was investigated. Nucleotide sequences of the interferon regulatory factor-1 gene and polymerase chain reaction products of its upstream region were determined directly and after cloning. The promoter activity of the upstream region of this gene was measured by the luciferase reporter assay. We found 4 point mutations in the upstream (- 1 approximately - 495) region, and the luciferase promoter assay demonstrated that these mutations did modify promoter activity. Analysis of DNA from healthy volunteers showed that these mutations are single nucleotide polymorphisms. These results suggest that single nucleotide polymorphisms of the interferon regulatory factor-1 promoter contribute, at least in part, to determining responses to type 1 interferons. J. Cell. Biochem. Suppl. 36: 191-200, 2001.

Antineoplastic Agents↗

PubMed2001

Reduction of telomerase activity in human liver cancer cells by a histone deacetylase inhibitor.

The presence of telomerase has been demonstrated recently in many different malignancies. Several reports documented that in human hepatocellular carcinoma, the level of telomerase activity parallels its differentiation stage. In the present study, the effect of the differentiation-inducing agent sodium butyrate on telomerase activity in four human liver cancer cell lines was investigated using the telomeric repeat amplification protocol. We assayed telomerase activity before and after butyrate treatment and in cell cycle synchronized non-dividing quiescent cells. In addition, telomerase reverse transcriptase levels were measured at the mRNA level. All four cell lines possessed high but not identical levels of telomerase activity. Telomerase activity was significantly reduced by treatment with sodium butyrate as well as trichostatin A in a dose- and time-dependent fashion, paralleling the reduction of cell proliferation. Although methotrexate, hydroxyurea, and colchicine synchronized the cell cycle at G1, S, and G2/M, respectively, and thereby also caused proliferating cells to cease dividing and become quiescent, in this case telomerase activity remained essentially unaltered compared to the control cultures. Moreover, levels of mRNA encoding telomerase reverse transcriptase were not always significantly altered by either sodium butyrate treatment or cell cycle synchronization. These results suggest that sodium butyrate, as a histone deacetylase inhibitor, effectively reduces telomerase activity without affecting transcription levels of the reverse transcriptase component.

Antineoplastic Agents↗

PubMed2001

Reduction of c-myc expression by an antisense approach under Cre/loxP switching induces apoptosis in human liver cancer cells.

c-Myc has been documented to be both a positive and a negative signal for the induction of apoptosis. It is well known that overexpression of the c-myc gene induces apoptosis of normal cells, but the result of a reduction in its expression is not fully understood. We examined whether a reduction in c-myc expression would induce apoptosis in human liver cancer cells. Specifically, antisense and sense oligodeoxynucleotides (oligos) against the human c-myc mRNA were synthesized, mixed with a liposome reagent at various ratios, and were applied to the liver cancer-derived cell lines, HCC-T, HepG2, and PLC/PRF/5. To exclude effects resulting from using oligos, plasmid vectors expressing the full-length c-myc cDNA in both sense and antisense orientations under the control of the Cre/loxP system were generated. Monoclonal cell lines including these plasmid vectors were produced and Cre was supplied by adenovirus infection. Apoptosis was determined morphologically and c-Myc and Bcl-2 expression was examined by Western blotting. The antisense myc significantly inhibited the proliferation of the cells within two days, while neither the liposome reagent alone nor sense myc did so. Most of the cells were rounded up by the antisense-treatment and nuclear fragmentation and DNA ladder formation were detected after two days in antisense c-myc-treated cells. Antisense c-myc largely reduced c-Myc and partially Bcl-2 expression; overexpression of Bcl-2 partially rescued from apoptosis in HCC-T and HepG2 cells. These results suggest that the massive reduction in c-myc mRNA induces apoptosis in liver cancer cell lines and consequent decrease in Bcl-2 enhances the cell death. c-Myc reduction under the Cre/loxP switching system may be a useful tool for the clarification of c-myc-related cellular mechanisms in differentiation and proliferation.

Apoptosis↗

PubMed2001

Steroid sulfatase expression in ovarian clear cell adenocarcinoma: immunohistochemical study.

OBJECTIVE: Steroid sulfatase (STS) is an important enzyme that converts biological inactive steroid sulfate to active free steroid. As estrogen is thought to play an important role in cell proliferation in gynecological cancer, the existence of STS may have particular significance in the prognosis of ovarian cancer. In the present study, we determined the STS expression of ovarian clear cell adenocarcinoma (OCCA), which has the poorest prognosis among various ovarian cancers, immunohistochemically to clarify the biological nature of OCCA and also to determine whether STS expression is one of the prognostic factors in OCCA. METHODS: Forty-five archival, formalin-fixed, paraffin-embedded tissues from patients with OCCA and other epithelial ovarian cancers who were first operated on from 1987 to 1998 were subjected to analysis. Twenty-eight of forty-five (60.9%) OCCA cases coexisted with endometriosis. They were subclassified into papillary, solid, and tubulocystic types with respect to architectural pattern. Immunohistochemical staining of STS was performed using anti-human STS polyclonal rabbit antibody that had been immunized with purified STS from human placenta. RESULTS: STS was immunohistochemically stained positively in 70% (32/45) of OCCA, 33.3% of serous adenocarcinoma (6/18), and 50.0% of mucinous adenocarcinoma (4/8) specimens and was localized in the cytoplasm of neoplastic epithelial cells. No significant relationship was found between STS staining and FIGO staging. However, patients diagnosed as papillary type had a significantly lower survival rate and showed significantly more positive staining of STS (P < 0.05) than those with solid type. Stage, STS expression, and architectural type yielded a significant association with survival rate. CONCLUSION: It was proven that STS is present in the cytoplasm of patients with OCCA by an immunohistochemical method. OCCA patients with papillary tumor with positive STS expression are considered to have a poor prognosis.

Adenocarcinoma, Clear Cell↗

PubMed2001

Expression of peptide transporter following intestinal transplantation in the rat.

BACKGROUND: The absorptive function of the intestinal graft is one of the most important factors for successful intestinal transplantation. To clarify whether the intestinal H(+)/peptide cotransporter (PEPT1) was expressed in the transplanted intestine, we examined the expression of PEPT1 in an experimental model of rat small intestinal transplantation in comparison with expression of Na(+)/glucose cotransporter (SGLT1). MATERIALS AND METHODS: Heterotopic intestinal transplantation was performed in allogeneic and syngeneic rat strain combinations. An additional group of allogeneic recipients was treated with tacrolimus (1 mg/kg) prior to transplantation, then daily for 7 days. Intestinal grafts were examined for histopathology and PEPT1 and SGLT1 expression. RESULTS: In the isografts, the levels of messenger RNA (mRNA) encoding both transporters were not changed, while the amount of SGLT1 protein was decreased and that of PEPT1 protein was increased. In the allografts, mRNA level and protein amount of both transporters and the amount of villin protein were decreased, and microscopic examination revealed histopathological features of rejection on day 7. Tacrolimus treatment ameliorated the histopathological features and prevented the decrease in villin protein expression. However, the decreases in PEPT1 and SGLT1 expression (both mRNA and protein) were partially prevented by tacrolimus treatment. CONCLUSION: This study indicated that the expression of transporters should be determined to evaluate intestinal graft function in addition to histopathological examination of the mucosa and that the levels of mRNA encoding intestinal nutrient transporters in biopsy specimens may be useful for evaluating the intestinal graft function for intestinal transplant patients.

Animals↗

PubMed2001

Effects of basic fibroblast growth factor on central nervous system functions.

Basic fibroblast growth factor (bFGF), initially identified as mitogens with prominent angiogenic properties, is now recognized as multifunctional growth factors with notable actions on neuronal cells. bFGF promotes the survival and neurite growth of brain neurons in vitro and in vivo, suggesting that it functions as a neurotrophic factor. This effect of bFGF could be beneficial for improving the survival of grafted neurons in transplantation. Furthermore, bFGF acutely modulates synaptic transmission in the hippocampus, suggesting that it has a role like a neurotransmitter or neuromodulator. In this article, we make a brief review of multiple biological activities of bFGF for brain neurons and discuss its potential usefulness for the treatment of neurodegenerative disorders including Alzheimer's disease and Parkinson's disease.

Animals↗

PubMed2001

Bronchial artery aneurysm treated with percutaneous transluminal coil embolization.

We present a case with asymptomatic mediastinal bronchial artery aneurysm at the origin of the left bronchial artery. This bronchial artery aneurysm was successfully treated with percutaneous transluminal coil embolization. Complete embolization of the feeding artery and tributaries from the aneurysm is the key to successful isolation of a large bronchial artery aneurysm from the circulation. Percutaneous transluminal embolization is one of the treatment options for a patient with asymptomatic, incidentally-identified bronchial artery aneurysm.

Aneurysm↗

PubMed2001

Posttreatment nadir M-protein level is a stronger discriminator of survival following plateau attainment than is percent reduction in M-protein in patients with IgG myeloma.

We conducted a retrospective study of patients with IgG or IgA myeloma who attained plateau to evaluate the relationships between survival and posttreatment nadir M-protein levels and between survival and the response to treatment evaluated by the percent reduction in M-protein. Of the 127 patients comprising 92 IgG and 35 IgA myeloma patients with disease stages II or III, 51 (40.2%) attained plateau. For IgG myeloma patients who attained plateau, survival time was not affected by the percent reduction in M-protein (median survival, 59.5 months for responding patients versus 54.4 months for nonresponding patients, P = .6910). Posttreatment nadir M-protein level, however, did affect survival time (median survival, 61.2 months for <3000 mg/dL versus 25.7 months for >3000 mg/dL, P = .0439). These findings suggest that the posttreatment nadir M-protein level is a stronger discriminator of survival following plateau attainment than the percent reduction of M-protein in patients with IgG myeloma.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2001

Novel synthesized trimannose conjugate induces endocytosis and expression of immunostimulatory molecules in monocytic leukemia cells.

Macrophage mannose receptor (MMR) recognizes the pattern of carbohydrates exposed on microorganisms and mediates endocytosis in macrophages. We have synthesized glycoconjugate cationic polymers carrying 3,6-branched alpha-D-mannoside, a trimannose conjugate (TMC) with a high affinity for mannose-specific lectins. Culture with 10 microM TMC for 6 hours induced adhesion and aggregation in NKM-1, a human myelomonocytic leukemia cell line. TMC also stimulated the accumulation of fluorescein isothiocyanate (FITC)-dextran (FITC-DX). This accumulation seemed to be mediated by endocytosis via MMR because mannan, which specifically binds to MMR, inhibited FITC-DX accumulation. Expression of CD14, adhesion molecules, and costimulatory molecules was induced for 24 hours in NKM-1 and in fresh leukemia blasts from 4 patients with acute myeloid leukemia (AML) M4 and M5 subtypes (French-American-British classification). To clarify the binding mechanism, we compared mannose conjugates and a monomer of mannose regarding their effects on endocytosis and enhancement of CD14 and CD86 expression. A polymer of monomannose clusters with a lower affinity for lectins slightly stimulated exdocytosis, whereas a monomer of trimannose had no effect. These findings suggest that concatenation between MMR and TMC may play an important role in the activation of monocytic leukemia cells. TMC may become a good candidate to target MMRs of leukemia cells.

Acute Disease↗

PubMed2001

Clinical trial to investigate the pharmacokinetics, pharmacodynamics, safety, and efficacy of recombinant factor VIIa in Japanese patients with hemophilia with inhibitors.

A multicenter and open-labeled clinical trial of human recombinant factor VIIa (rFVIIa) was conducted in Japanese patients with severe hemophilia A or B with inhibitors. The trial consisted of 2 parts. In study 1, the pharmacokinetics, pharmacodynamics, and safety of a single dose of 120 microg/kg of rFVIIa were investigated in 8 patients. In the subsequent study 2, the hemostatic effect and safety of rFVIIa were evaluated during a 24-week period in 10 patients. In study 1, the mean maximum FVII-coagulant activity (FVII:C) was found to occur after 10 minutes; activity then decreased rapidly and returned to the baseline within 24 hours after a single intravenous infusion of rFVIIa. The mean half-life of FVII:C was 3.5 hours. The activated partial thromboplastin time and prothrombin time in the patients were immediately shortened but returned to the baseline within 24 hours after dosing. In study 2, 86 microg/kg to 120 microg/kg of rFVIIa (mean, 97 microg/kg) was administered 1 to 85 times to 10 patients. A total of 58.0% (91/157) of bleeding episodes were treated excellently or effectively, with 5 (3.2%) ineffective episodes. There was no apparent trend in the relationship of the hemostatic effect with bleeding sites, mean dose, or number of injections. The efficacy rate, however, was significantly higher (90.0%) in bleeding episodes treated within 3 hours than in those treated at longer intervals (31.0%). No treatment-related adverse events were observed, and there was no evidence of antibody formation to rFVIIa. In conclusion. rFVIIa is an effective and well-tolerated option for treatment of bleeding episodes in hemophilia patients with inhibitors.

Adolescent↗

PubMed2001

Population pharmacokinetics of tacrolimus in adult recipients receiving living-donor liver transplantation.

OBJECTIVE: To characterize the pharmacokinetics of tacrolimus in adult recipients receiving living-donor liver transplantation (LDLT). METHODS: Thirty-five patients were given tacrolimus as 18- to 60-h intravenous infusions after surgery, followed by a 4-week course of oral dose therapy (at 0900 hours and 2100 hours). Blood samples were collected daily in the morning (0800 hours) beginning the day after surgery. Whole blood concentration data were evaluated by nonlinear mixed-effect modeling using the program NONMEM and were characterized using a one-compartment model. RESULTS: The clearance (CL, l h(-1)) was related to the grafted hepatic weight, postoperative days (POD), and hepatic and renal dysfunction. Interindividual variabilities in CL, volume of distribution (V), and bioavailability (F) were 57.4%. 39.7%, and 63.0%, respectively, and the correlation between individual CL and F was 0.776. Residual intraindividual variability was 2.9 ng ml(-1). Based on the estimated final parameters, a typical recipient of LDLT with grafted hepatic weight of 600 g and normal hepatic and renal function would have a CL of 0.737 l h(-1) on POD 0 and 1.14 l h(-1) on POD 30, V of 1.52 l kg(-1) and F of 6.8%. CONCLUSIONS: Nonlinear mixed-effect modeling was useful for analysis of pharmacokinetic characteristics of tacrolimus in LDLT patients. Immediately after surgery, patients receiving LDLT showed a smaller CL value than other transplant patients, and CL value increased with POD within 30 days after surgery. The estimated population pharmacokinetic parameters can be applied for a priori dosage calculations in adult patients with LDLT.

Adolescent↗

PubMed2001

FLT3 tyrosine kinase as a target molecule for selective antileukemia therapy.

Fusion gene products such as PML-RARalpha and BCR-ABL generated by leukemia-specific chromosomal translocations have been identified as target molecules for the treatment of leukemia. Here we describe one possibility for extending the frontier of mechanism-based medicine for acute myeloid leukemia (AML). FLT3, a receptor tyrosine kinase (RTK) preferentially expressed in hematopoietic progenitor cells, frequently has a gain-of-function mutation in AML. To search for FLT3-targeted compounds, we screened the growth-inhibitory effects of several tyrosine kinase inhibitors (TKIs) on mutant FLT3-transformed 32D cells. Herbimycin A at a concentration of 0.1 microM markedly inhibited the growth of the transfectants but at that concentration was ineffective in parental 32D cells. It suppressed the constitutive tyrosine phosphorylation of the mutant FLT3, but not the phosphorylation of the ligand-stimulated wild-type FLT3. In mice transplanted with transformed 32D cells, the administration of herbimycin A completely prevented leukemia progression. Recent studies have indicated that herbimycin A binds directly with HSP90, a molecular chaperone, and destabilizes HSP90-associated proteins. Another HSP90 inhibitor, radicicol, also induced apoptosis selectively in transformed 32D cells. HSP90 is a promising target for the treatment of AML with mutant FLT3.

Acute Disease↗

PubMed2001

Mortality and cancer incidence among a population previously exposed to environmental cadmium.

OBJECTIVES: This paper evaluates the associations of previous exposure to environmental cadmium (Cd) and renal function with total mortality and cancer incidence. METHODS: The study population comprised 275 residents (aged 40-92 years at baseline) in a Cd-polluted area located on Tsushima Island, Nagasaki, Japan. In the study area, the dietary intake of Cd decreased because the soil of the Cd-polluted rice fields was replaced with new soil between 1980 and 1983. The mortality rate from 1982 to 1997 and cancer incidence from 1985 to 1996 were investigated. Standardized mortality and incidence ratios (SMR and SIR) were calculated by using regional reference rates. The associations of renal function and urinary Cd levels with total mortality and cancer incidence were evaluated with Cox regression models. RESULTS: The SMR for all subjects, and those with a urinary beta2-microglobulin (U-beta2M) concentration > or = 1,000 microg/g creatinine (Cr) and < 1,000 microg/g Cr was estimated at 90 [95% confidence interval (CI) 73-109], 138 (95% CI 101-183) and 66 (95% CI 49-87), respectively. After adjustment for age and other potential confounders, in men, serum beta2M (S-beta2M) (> or = 2.3 mg/l) and in women, serum Cr (> or = 21.2 mg/ 100 ml), relative clearance of beta2M (> or = 21%) and U-beta2M (> or = 1,000 microg/g Cr), were associated with a significantly increased risk of mortality, with hazard ratios exceeding 2.0. After further adjustment for log(U-beta2M), the rate ratio of deaths associated with, in men, increased S-beta2M was 2.53 (95% CI 0.97-6.65) and, in women, increased serum Cr (S-Cr) concentrations was 2.75 (95% CI 1.24-6.14). Urinary Cd concentrations (> or = 10 microg/g Cr) were not significantly associated with mortality. The overall SIR of all malignant neoplasms was 71 (95% CI 44-107). CONCLUSIONS: These findings suggest that renal tubule dysfunction and a reduced glomerular filtration rate are predictors of mortality among persons previously exposed to environmental Cd. However, the results also suggest that overall mortality rates in Cd-polluted areas are not necessarily increased, because of the low mortality among those with no, or only slight, signs of low-molecular weight proteinuria. Overall cancer incidence may not be increased among residents in Cd-polluted areas.

Adult↗

PubMed2001

Distinct transport characteristics of basolateral peptide transporters between MDCK and Caco-2 cells.

The cellular polarity of [14C]glycylsarcosine (Gly-Sar) transport in Madin-Darby canine kidney (MDCK) cells was compared with that in the human intestinal cell line Caco-2. In MDCK cells, [14C]Gly-Sar accumulation was greater at the basolateral side than at the apical side, and there was little net transcellular transport. In Caco-2 cells, [14C]Gly-Sar accumulation was greater at the apical side and unidirectional transcellular transport occurred from the apical to basolateral side. Efflux of [14C]Gly-Sar from MDCK cells to either side was negligible, whereas that from Caco-2 cells was significantly faster to the basolateral side. The basolateral peptide transporter in MDCK cells possessed a similar substrate specificity, but a much higher substrate affinity, than that in Caco-2 cells. The basolateral peptide transporter in MDCK cells did not accumulate Gly-Sar during hypertonic stress. These findings indicate that the basolateral peptide transporter in MDCK cells is involved in the cellular uptake of small peptides, but not in the extrusion of small peptides to the extracellular space.

Animals↗