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Biomedical subjects

M Yasuhara

Publications and source records attributed to M Yasuhara.

At least 19 recordsLinked to original sources
PubMed1992

Transport of procainamide in a kidney epithelial cell line LLC-PK1.

Transport of procainamide, an anti-arrhythmic drug, was investigated in LLC-PK1 kidney epithelial cell line. The uptake of procainamide by LLC-PK1 monolayers cultured in plastic dishes was temperature-dependent, saturable and inhibited by organic cations such as cimetidine and N-acetylprocainamide. An aminocephalosporin antibiotic, cephalexin, also inhibited procainamide uptake, but an organic anion, p-aminohippurate, did not. The uptake of procainamide was greater at an alkaline external pH than at an acidic pH. In addition, procainamide uptake increased when intracellular pH was decreased and the uptake decreased when the intracellular pH was increased by ammonium chloride treatment, indicating the involvement of an H+/procainamide antiport system in apical membrane. The basolateral to apical flux of procainamide across LLC-PK1 monolayers cultured on permeable supports was 2.5-times larger than the apical to basolateral flux, and only the former process was inhibited by other organic cations. These findings suggest that LLC-PK1 cells can transport procainamide by the organic cation transport system and that procainamide is transported unidirectionally from basolateral to apical side across the cell monolayers.

Animals↗
PubMed1992

Expression of renal organic cation transporter in Xenopus laevis oocytes.

The expression of the organic cation transport system of rat renal proximal tubules has been studied in Xenopus laevis oocytes injected with poly(A)+ RNA from the rat renal cortex. The effectiveness of the technique was confirmed by examining expression of the Na+/D-glucose co-transporter. Compared with water-injected and non-injected oocytes, the injection of total poly(A)+ RNA resulted in about a 3-fold increase in tetraethylammonium (TEA) uptake activity. TEA uptake by poly(A)(+)-RNA-injected oocytes was time-dependent and was inhibited by cimetidine and HgCl2, but not by p-aminohippurate. After size-fractionation on a sucrose density gradient, a 1.4-2.4 kb poly(A)+ RNA fragment was identified that expressed the organic cation transport system in oocytes. These results demonstrate that the renal organic cation transporter was expressed in oocytes and that this expression system can provide an effective assay procedure for cloning of the organic cation transporter.

Animals↗
PubMed1992

A comparative study on immunosuppressive effects of cyclosporin A and FK 506 on peripheral blood lymphocytes in dogs.

Immunosuppressive effects of cyclosporin A (CsA) and FK 506 (FK) on peripheral blood lymphocytes were studied in dogs in respect to mixed lymphocyte reaction, proliferative responses to recombinant interleukin-2 (rIL-2), phytohemagglutinin (PHA) and concanavalin-A (Con-A); phenotypes of OKIa1, CD3, CD8 and surface IgM; cytotoxic activity against xenogeneic tumor cells. CsA (2.0 or 5.0 mg/kg, intravenously) or FK (0.16 mg/kg, intramuscularly) was given to mongrel dogs every morning for serial 21 days. The blood concentrations of CsA, measured as trough levels by fluorescence polarization method, ranged from 37 to 350 ng/ml in dogs administered at 2.0 mg/kg and from 170 to 894 ng/ml in dogs administered at 5.0 mg/kg during treatment, respectively. In dogs treated with FK at a dose of 0.16 mg/kg, the drug concentrations in the plasma during treatment ranged from 0.16 to 1.8 ng/ml. Mixed lymphocyte reaction and proliferative responses to rIL-2, PHA and Con-A, which were declined by CsA, were not affected by FK. In contrast, the proportion of OKIa1+ cells was not affected by CsA, whereas FK decreased the proportion of OKIa1+ cells progressively during the course of treatment. Cytotoxic activity was suppressed by both CsA and FK. These results possibly indicate that CsA and FK exert their immunosuppressive effects via different mechanisms.

Animals↗
PubMed1992

Effect of leukotriene C4 on theophylline disposition in guinea pigs.

The pharmacokinetics of theophylline in acutely ill patients show wide intraindividual variability associated with the severity of clinical status. To investigate the mechanism of this variability, we studied the effects of leukotriene C4 (LTC4)-induced pathophysiologic changes on the disposition of theophylline. The plasma concentration-time profiles were measured after simultaneous intravenous bolus injection of theophylline and antipyrine in guinea pigs. The animals received 5 micrograms/kg of LTC4 intravenously 60 min later. The plasma theophylline concentration 30 min after LTC4 treatment was significantly lower (p less than 0.05) than that of nontreated control animals, whereas the plasma antipyrine concentration at that time was not affected. In addition, the treated animals showed significantly slower declines in plasma concentrations of both drugs (0.0805 +/- 0.0199 and 0.291 +/- 0.020 h-1 for theophylline and antipyrine, respectively, mean +/- SEM) than did controls (0.197 +/- 0.010 and 0.439 +/- 0.028 h-1). Leukotriene C4 treatment also induced moderate bronchoconstriction and metabolic acidosis, increased blood hemoglobin concentration and hematocrit, and decreased concentration of serum proteins. In connection with these changes, the plasma unbound fraction of theophylline increased significantly (p less than 0.001, 94.4 +/- 3.3% in treatment versus 58.2 +/- 4.4% in control), but that of antipyrine was unchanged (94.9 +/- 3.0% in treatment versus 92.1 +/- 0.9% in control). These findings indicated that an increase in the volume of distribution was responsible for the abrupt change in plasma theophylline concentration following LTC4 treatment, and the apparent change in the volume of distribution was estimated as 26.1 +/- 5.6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminophylline↗
PubMed1992

Pharmacokinetics of brain natriuretic peptide in rats.

The pharmacokinetics of rat brain natriuretic peptide (rBNP) was compared with that of alpha-rat atrial natriuretic peptide (alpha-rANP) in rats. After intravenous infusion in rats (600 pmol min-1kg-1 for 2 min), the disappearance of plasma rBNP was 4-fold slower than that of alpha-rANP. The estimated mean plasma clearance rates for rBNP and alpha-rANP were 45.9 ml min-1kg-1 and 74.4 ml min-1kg-1, respectively. The affinity of rBNP for the clearance receptor or degradation enzyme was considered to be lower than that of alpha-rANP.

Animals↗
PubMed1992

Mechanisms of pharmacokinetic interaction between propranolol and quinidine in rats.

In order to study the mechanism of propranolol-quinidine interaction, the effects of quinidine on propranolol pharmacokinetics were examined in male Wistar rats. The concurrent oral administration of quinidine (10 mg/kg) markedly increased the plasma concentration of propranolol (2.5 mg/kg), and the area under the propranolol concentration-time curve increased about 3.6-fold. These results are consistent with previous observations in man and indicate the possible usefulness of the male Wistar rat as an animal model for investigating the mechanisms of the drug interaction. When propranolol was given intravenously, a concurrent administration of quinidine increased the apparent distribution volume of propranolol, mainly by decreasing its plasma protein binding. However, the systemic clearance of propranolol was not significantly altered by quinidine. Thus, quinidine increased the availability of oral propranolol from 13.8 +/- 2.2 to 44.2 +/- 4.6% (p less than 0.01). Furthermore, quinidine delayed the elimination of propranolol from the isolated perfused rat liver. These results indicate that quinidine reduces the presystemic elimination of propranolol in the liver, thereby increasing its systemic availability after oral administration.

Animals↗
PubMed1992

Inhibition of apical membrane enzyme activities and protein synthesis by gentamicin in a kidney epithelial cell line LLC-PK1.

The mechanism of a gentamicin-induced decrease in apical membrane enzyme activities was investigated in LLC-PK1 cells. Increasing activities of apical membrane enzymes (alkaline phosphatase, aminopeptidase, and gamma-glutamyltransferase) were markedly suppressed by gentamicin during growth in culture. On the other hand, a lesser effect was observed when the activities of these enzymes were decreasing or relatively constant. Gentamicin treatment decreased the maximal enzyme activities of alkaline phosphatase and aminopeptidase, indicating that the number of active enzyme molecules in the apical membrane was decreased by gentamicin. [3H]Leucine incorporation in LLC-PK1 cells was inhibited by gentamicin in a dose-dependent manner, followed by a reduction of total protein. In addition, a well-known protein synthesis inhibitor, cycloheximide, also decreased the apical enzyme activities. These results suggest that the inhibition of protein synthesis by gentamicin is a possible cause of the decreased activities of apical membrane enzymes in LLC-PK1 cells. The inhibition of protein synthesis may be related to the nephrotoxicity induced by aminoglycoside antibiotics.

Animals↗
PubMed1992

A statistical study on clinical findings of solar keratosis.

Clinical findings were studied in 50 patients with 53 lesions of solar keratosis encountered during the 15 year period from 1977 to 1991. The majority of these cases were evident in the over-sixty age group (average 62.2 years). A greater proportion were females. Most lesions were observed on the face; especially on the cheek, and from the outer eyelid to the temple. The erythematous type (desquamative-keratotic) lesion was the most evident. With the exceptions of the years 1979 and 1991, no remarkable increase in the number of patients was noted during the 15 year period.

Adult↗
PubMed1992

A statistical study on histopathologic findings of solar keratosis.

We examined histopathologic data from 50 patients with 53 lesions of solar keratosis encountered over the past 15 years (1977 to 1991). The epidermis showed acanthosis, uneven epidermal dyeing properties, disorderly arrangement of the basal cells, atypia of the nucleus, mitotic figures and hyperpigmentation of the basal layers. The dermis showed actinic elastosis, cell infiltration mainly consisting of the lymphoid cells, and incontinentia pigmenti histologica. Among histologic types, the hypertrophic type was the primary example.

Adult↗
PubMed1992

Reciprocal changes in serum levels of immunoglobulins (IgG, IgA, IgM) and complements (C3, C4) in normal pregnancy and after delivery.

Sequential changes in serum levels of IgG, IgA, and IgM, and C3 and C4 during and after pregnancy were studied in 8 healthy women. Serum IgG decreased gradually during pregnancy, but increased markedly during the six months following delivery. Serum IgA and IgM levels also showed patterns similar to IgG. In contrast, C3 and C4 levels increased significantly and reached maximum levels in the last trimester during pregnancy, but decreased gradually for six months after delivery. Reciprocal changes between immunoglobulins and complements were clarified for the first time, and were suggestive of a compensatory autoregulatory mechanism in the suppression of the humoral immune system during pregnancy.

Adult↗
PubMed1992

Transport of digoxin by human P-glycoprotein expressed in a porcine kidney epithelial cell line (LLC-PK1).

This article represents the first evidence that the renal secretion of the commonly used drug, digoxin, is mediated by P-glycoprotein. In this study, it was demonstrated that digoxin is a substrate of P-glycoprotein, and the mechanism of a clinically important drug interaction, such as digoxin-quinidine, was elucidated. Human P-glycoprotein was expressed on the apical membrane of the porcine kidney epithelial cell line, LLC-PK1 by transfecting with human MDR1 cDNA. The expression and function of P-glycoprotein were confirmed by Southern and Western blotting, RNase protection assay, immunostaining and transporting activity for vinblastine. The transepithelial transport of [3H]digoxin was measured across the cell monolayers grown on microporous polycarbonate membrane filters. The transfectant cells exhibited markedly greater basal-to-apical transport and less apical-to-basal transport than the host cells, and the former was 8-fold greater than the latter. The augmented transepithelial transport resulted from the increased efflux from cells to apical side. This oriented transport was inhibited by the presence of 20 microM vinblastine, quinidine or verapamil. The rate of efflux to the apical side was 2-fold greater than that to the basal side. Quinidine inhibited the efflux to the apical side but did not affect transport into the basal side. These findings demonstrate that digoxin is transported by human P-glycoprotein, which is a previously undiscovered drug transport system in the kidney other than organic cation and anion transport systems, and suggest a molecular mechanism for the renal tubular secretion of digoxin as well as clinically important digoxin-quinidine interaction via P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Surface binding and intracellular uptake of gentamicin in the cultured kidney epithelial cell line (LLC-PK1).

Aminoglycoside antibiotics such as gentamicin are taken up by renal proximal tubular cells, yet little is known regarding the biochemical characteristics of the transport process at the cellular level. In this report, cellular handling of gentamicin was studied in the cultured kidney epithelial cell line LLC-PK1. After 2 days of incubation of the cells with gentamicin, cell-associated gentamicin decreased rapidly during the first 30 min when the cells were incubated in gentamicin-free medium, then decreased slowly. The apparent half-life of the latter phase, which should represent release from the intracellular compartment, was about 2.0 days. The rapid release of gentamicin should consist of two components, one is a release from the cell surface membrane and the other from domes. Cell surface binding of gentamicin was dependent on the ambient ionic strength. The intracellular uptake was inhibited by low temperature, neomycin, metabolic inhibitors and reagents which interact with the cytoskeleton. On the other hand, the uptake was not affected by d-glucose, organic cations and an organic anion. Thus, by estimating the intracellular gentamicin separately from the drug localized in other compartments, it is concluded that gentamicin is taken up by LLC-PK1 cells via an adsorptive endocytosis. The endocytosis of gentamicin should be dependent on metabolic energy and cytoskeletal function.

Animals↗
PubMed1991

Deficiency of apolipoprotein B synthesis in Suncus murinus.

We reported previously that fatty liver is easily induced in a novel experimental animal, Suncus murinus (suncus) by withholding food. In this study, we focused on lipoprotein and apolipoprotein secretion from the liver. The study of lipoproteins from this animal revealed that small amounts of lipoproteins with apolipoprotein (apo) E but without apo B were observed in the fraction of density less than 1.08 g/ml. In order to learn whether apo B is synthesized by the liver or not, isolated suncus livers were perfused with an addition of [35S]methionine. Small amounts of radioactivity were observed in apo E of VLDL, and fairly large amounts in apo E and A-I in the fraction of LDL + HDL, suggesting that VLDL was secreted with apo E but not with apo B from the liver. Northern blot analysis with use of rat apo B cDNA revealed a weak signal of hybridized rat apo B cDNA between 15 kb and 9 kb in the suncus liver and intestinal mucosa; this is almost the same size as rat apo B mRNA. This finding suggests the presence of apo B mRNA in the suncus. In conclusion, apo B is not secreted from the suncus liver, owing to a defect in intracellular post-transcriptional processing or to ineffective transcription. This might be one of the reasons for fatty deposits in the suncus liver. Suncus may be a candidate for an animal model of abetalipoproteinemia as well as fatty liver due to a defect of apo B synthesis.

Animals↗
PubMed1991

Acetaldehyde metabolism in different aldehyde dehydrogenase-2 genotypes.

In order to clarify the relationships between acetaldehyde (Ac-CHO) metabolism and low Km (mitochondrial) aldehyde dehydrogenase (ALDH2) genotypes, hepatic ALDH2 activity was determined and serial changes of blood Ac-CHO levels after ethanol administration were analyzed in the individuals homozygous for the normal ALDH2 genes, heterozygous for the normal and mutant ALDH2 genes, and homozygous for the mutant ALDH2 genes. Genomic DNA was extracted from white blood cells and genotyping of ALDH2 was performed using the polymerase chain reaction technique and slot blot hybridization with synthesized oligonucleotide probes specific to the normal and mutant ALDH2 genes. ALDH2 activity was not detectable in the liver in two cases of the mutant homozygote. In four out of eight cases of the heterozygote, hepatic ALDH2 activity was measurable, although the activity was lower compared with that in the normal homozygote. Blood ethanol levels after alcohol administration were not different among the three different ALDH2 genotypes. Blood Ac-CHO levels after drinking of alcohol were significantly higher in the heterozygotes and the mutant homozygotes than in the normal homozygotes. The levels after a moderate amount of ethanol (0.8 g/kg of body weight) in a case of the mutant homozygote were not different from those of the heterozygotes. However, the levels after a small amount of ethanol (0.1 g/kg of body weight) were significantly higher in the mutant homozygotes than in the heterozygotes. These results indicate that hepatic ALDH2 activity is lacking completely, and metabolism of Ac-CHO in the liver is severely impaired in the homozygotes of the mutant ALDH2 genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1991

[Converse changes in serum levels of immunoglobulins (IgG, A and M) and complement components (C3, 4) during pregnancy].

Sequential changes in serum levels of the immunoglobulins IgG, A and M and of the complements C3 and C4 during pregnancy and the postpartum period were studied in 8 healthy women. Serum IgG and A levels decreased gradually during pregnancy, but increased significantly during the first three months following delivery. Serum IgM level also decreased during pregnancy, reaching its minimum during the second trimester, but increased thereafter. In contrast, C3 and C4 levels increased significantly during pregnancy and reached their maximum levels during the last trimester. After delivery, levels of these two components decreased gradually for the next six months. The complement system may operate as a compensatory autoregulatory mechanism in the suppression of the humoral immune system during pregnancy.

Adult↗