Biomedical subjects

T Imai

Publications and source records attributed to T Imai.

At least 289 records · Page 16Linked to original sources

PubMed1998

Expression of NPAT, a novel substrate of cyclin E-CDK2, promotes S-phase entry.

To understand the mechanisms by which CDKs regulate cell cycle progression, it is necessary to identify and characterize the physiological substrates of these kinases. We have developed a screening method to identify novel CDK substrates. One of the cDNAs identified in the screen is identical to the recently isolated NPAT gene. Here we show that NPAT associates with cyclin E-CDK2 in vivo and can be phosphorylated by this CDK. The protein level of NPAT peaks at the G1/S boundary. Overexpression of NPAT accelerates S-phase entry, and this effect is enhanced by coexpression of cyclin E-CDK2. These results suggest that NPAT is a substrate of cyclin E-CDK2 and plays a role in S-phase entry.

CDC2-CDC28 Kinases↗

PubMed1998

DSIF, a novel transcription elongation factor that regulates RNA polymerase II processivity, is composed of human Spt4 and Spt5 homologs.

We report the identification of a transcription elongation factor from HeLa cell nuclear extracts that causes pausing of RNA polymerase II (Pol II) in conjunction with the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB). This factor, termed DRB sensitivity-inducing factor (DSIF), is also required for transcription inhibition by H8. DSIF has been purified and is composed of 160-kD (p160) and 14-kD (p14) subunits. Isolation of a cDNA encoding DSIF p160 shows it to be a homolog of the Saccharomyces cerevisiae transcription factor Spt5. Recombinant Supt4h protein, the human homolog of yeast Spt4, is functionally equivalent to DSIF p14, indicating that DSIF is composed of the human homologs of Spt4 and Spt5. In addition to its negative role in elongation, DSIF is able to stimulate the rate of elongation by RNA Pol II in a reaction containing limiting concentrations of ribonucleoside triphosphates. A role for DSIF in transcription elongation is further supported by the fact that p160 has a region homologous to the bacterial elongation factor NusG. The combination of biochemical studies on DSIF and genetic analysis of Spt4 and Spt5 in yeast, also in this issue, indicates that DSIF associates with RNA Pol II and regulates its processivity in vitro and in vivo.

Amino Acid Sequence↗

PubMed1998

Platelet-activating factor receptor antagonist attenuates endotoxin-induced vascular hyporeactivity in the pithed rat.

The role of platelet activating factor (PAF) and nitric oxide (NO) in the endotoxin-induced hyporeactivity to noradrenaline was studied in the pithed rat. Pressor dose-response curves to noradrenaline (0.01-10 microg/kg, i.v.) were made starting 1 h after the administration of endotoxin (0.5 mg/kg, i.v.) to the rats. Saline was administered to the control rats. The PAF receptor antagonist, TCV-309 (3-bromo-5-[N-phenyl-N-[2-[[2-(1,2,3,4-tetrahydro-2-isoquinolylcarbon yloxy)ethyl]carbamoyl]ethy]carbamoyl]-1-propylpyridinium nitrate, 100 microg/kg, i.v.), or the NO synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA, 30 mg/kg, i.v.), was administered to the endotoxin-treated rats 20 or 10 min before the noradrenaline challenge. L-NMMA reversed endotoxin-induced hyporeactivity completely. TCV-309 produced a significant, but partial attenuation of the hyporeactivity to noradrenaline (P < 0.01). There was still significant hyporeactivity when compared with the control rats (P < 0.01) and the L-NMMA-treated endotoxin-administered rats (P < 0.05). These data suggest that endogenous PAF contributes to the vascular hyporeactivity to noradrenaline induced by endotoxin and that NO plays a major role in the endotoxin-induced hyporeactivity.

Animals↗

PubMed1998

Macrophage-derived chemokine is a functional ligand for the CC chemokine receptor 4.

Macrophage-derived chemokine (MDC) is a recently identified member of the CC chemokine family. MDC is not closely related to other chemokines, sharing most similarity with thymus- and activation-regulated chemokine (TARC), which contains 37% identical amino acids. Both chemokines are highly expressed in the thymus, with little expression seen in other tissues. In addition, the genes for MDC and TARC are encoded by human chromosome 16. To explore this relationship in greater detail, we have more precisely localized the MDC gene to chromosome 16q13, the same position reported for the TARC gene. We have also examined the interaction of MDC with CC chemokine receptor 4 (CCR4), recently shown to be a receptor for TARC. Using a fusion protein of MDC with secreted alkaline phosphatase, we observed high affinity binding of MDC-secreted alkaline phosphatase to CCR4-transfected L1.2 cells (Kd = 0.18 nM). MDC and TARC competed for binding to CCR4, while no binding competition was observed for six other chemokines (MCP-1, MCP-3, MCP-4, RANTES (regulated on activation normal T cell expressed and secreted), macrophage inflammatory protein-1 alpha, macrophage inflammatory protein-1 beta). MDC was tested for calcium mobilization in L1.2 cells tranfected with seven different CC chemokine receptors. MDC induced a calcium flux in CCR4-transfected cells, but other receptors did not respond to MDC. TARC, which also induced calcium mobilization in CCR4 transfectants, was unable to desensitize the response to MDC. In contrast, MDC fully desensitized a subsequent response to TARC. Both MDC and TARC functioned as chemoattractants for CCR4 transfectants, confirming that MDC is also a functional ligand for CCR4. Since MDC and TARC are both expressed in the thymus, one role for these chemokines may be to attract CCR4-bearing thymocytes in the process of T cell education and differentiation.

Calcium↗

PubMed1998

ATM mutations in patients with ataxia telangiectasia screened by a hierarchical strategy.

ATM has been identified as a gene that is responsible for ataxia telangiectasia (AT), a pleiotropic disorder of autosomal recessive inheritance. While many mutations of this gene in AT patients of various ethnicities have been reported, data on Japanese patients are scarce. In this report, we present the results of a thorough survey of ATM mutations in 14 unrelated AT patients, with an emphasis on Japanese subjects. We used a hierarchical strategy in which we extensively analyzed the entire coding region of the cDNA. In the first stage, point mutations were sought by PCR-SSCP in short patches. In the second and third stages, the products of medium- and long-patch PCR, each covering the entire region, were examined by agarose gel electrophoresis to search for length changes. We found a total of 15 mutations (including 12 new) and 4 polymorphisms. Abnormal splicing of ATM was frequent among Japanese, and no hotspot was obvious, suggesting no strong founder effects in this ethnic group. Eleven patients carried either one homozygous or two compound heterozygous mutations, one patient carried only one detectable heterozygous mutation, and no mutation was found in two patients. Overall, mutations were found in at least 75% of the different ATM alleles examined. Possible reasons for the inability to detect mutations in some patients are discussed.

Ataxia Telangiectasia↗

PubMed1998

A lymphocyte-specific CC chemokine, secondary lymphoid tissue chemokine (SLC), is a highly efficient chemoattractant for B cells and activated T cells.

Secondary lymphoid tissue chemokine (SLC) is a CC chemokine expressed mainly in lymph nodes, appendix and spleen, and specifically chemotactic for lymphocytes (Nagira et al., J. Biol. Chem. 1997. 272: 19518-19524). Here, we carried out transendothelial migration assays to determine the classes and subsets of lymphocytes migrating toward SLC. SLC attracted freshly isolated B cells with high efficiency and T cells modestly. Thus, SLC is the first CC chemokine with a strong chemotactic activity on fresh B cells. Among T cell types and subsets, SLC broadly attracted CD4+ and CD8+ cells, CD45RO- (naive) and CD45RO+ (memory) cells, and CD26high (activated) and CD26low- (resting) cells. SLC also attracted both L-selectin+ and L-selectin- subpopulations of various T cell subsets and B cells. Furthermore, mitogenic stimulation strongly enhanced migratory responses of T cells and B cells toward SLC. By in situ hybridization, SLC mRNA was detected in the cortical parafollicular regions (the T cell areas) of a lymph node and an appendix. Collectively, SLC may be a basic chemokine supporting homeostatic migration of a broad spectrum of lymphocytes into the secondary lymphoid tissues. SLC may also be involved in immune responses by inducing highly efficient migration of T and B cells following antigenic stimulation.

Adult↗

PubMed1998

Heating rate of egg albumin solution and its change during Ohmic heating.

Ohmic heating of egg albumin solution (10 w/v%) was examined at 50-10 kHz under a constant 10 V/cm. The heating rate of the solution was almost constant and increased slightly as the frequency increased. The gel formation was observed at about 75 degrees C and the heating rate increased above this temperature irrespective of the frequency used. The solution and gel showed almost the same impedance at the examined temperature (20-90 degrees C) and frequency (10 Hz-100 kHz). When the concentration of egg albumin was reduced to 2 w/v%, no gel was formed and a constant heating rate at over 75 degrees C was observed. The breaking strength of the gels showed little difference among the gels prepared by boiling water or Ohmic heating. These results suggest that the liquid components are not compartmentalized in the gel and that the sudden increase of heating rate above 75 degrees C was caused by the reduction of heat transfer of the gel at its phase change to the gel. Ohmic heating was also applied to the fresh egg white at the same conditions as that of the egg albumin solution. The fresh egg white did not show any sudden increase of heating rate until it reached 90 degrees C. However, the homogenized fresh egg white and its soluble part separated beforehand showed a slightly reduced heating rate and a sudden increase at about 60 degrees C. These results suggest that the gelatinous component of fresh egg white such as ovomucin represses the transfer of generated heat during Ohmic heating.

Animals↗

PubMed1998

Anaesthesia affects outcome of sepsis in mice.

PURPOSE: To determine whether the survival curves and rates differ between a mutant strain of mice (C3H/HeJ: endotoxin-resistant) and an endotoxin-susceptible strain (C3H/HeN) when severe sepsis (caecal ligation and puncture: CLP) is performed with different anaesthetics (ketamine or varied exposure to halothane). METHODS: The CLP was performed under a randomly chosen anaesthetic method out of inhalation of halothane in oxygen (15 min, 2 hr, or 6 hr) (100, 120, and 103 mice respectively) or a single injection of ketamine im (127 mice) in paired fashion in eight-week-old male mice of each strain. The daily survival rates were compared between the two strains until the 10th day after CLP for each anaesthetic and among the four anaesthetic methods for each strain using multiple comparisons. RESULTS: The C3H/HeJ had delayed death relative to the C3H/HeN with every anaesthetic method except a two hours halothane (P < 0.01 at day 1 and day 2-5 in halothane 15 min and 6 hr, P < 0.05 at day 4-6 in ketamine), however, the final survival rates for each method of anaesthesia were the same in the two strains. Regardless of the genetic susceptibility to endotoxin, short exposure to halothane resulted in the most rapid death compared with the other anaesthetic methods (P < 0.05), and two hours halothane showed the best survival. CONCLUSION: Endotoxin susceptibility affected the septic course for each anaesthetic method, and the anaesthetic methods influenced the survival from sepsis in both strains.

Anesthesia↗

PubMed1998

Parathyroid hormone suppression by 22-oxacalcitriol in the severe parathyroid hyperplasia.

The suppression of parathyroid hormone (PTH) secretion by the administration of 1,25-dihydroxyvitamin D [1,25(OH)2D3] and 22-oxacalcitriol (OCT) was evaluated in nude mice transplanted with human hyperplastic parathyroid tissue. The parathyroid tissue was obtained for transplantation from a patient with severe secondary hyperparathyroidism who had undergone a parathyroidectomy. Tissue specimens were transplanted into the gluteus muscle of female nude mice. Animals were divided into two groups; one group was fed a normal diet, and the other group was fed a low calcium diet during the administration of OCT and 1,25(OH)2D3. OCT and 1,25(OH)2D3 were intraperitoneally administered two times every week, for a total of eight times. Serum calcium and phosphate levels were significantly higher in the mouse administered 1,25(OH)2D3 than in the mouse administered OCT. Serum alkaline phosphatase activity was elevated similarly in the mouse administered either OCT or 1,25(OH)2D3. OCT strongly suppressed human PTH secretion from the graft in mice with normal serum calcium levels as did 1,25(OH)2D3. However, human PTH secretion from the graft was stimulated by the administration of a low-calcium diet, despite OCT and 1,25(OH)2D3 administration. In summary, OCT and 1,25(OH)2D3 suppress PTH secretion even from severe secondary hyperplastic parathyroid tissue only in mice with normal or high calcium serum levels.

Alkaline Phosphatase↗

PubMed1998

Estimation of regional lung function in interstitial pulmonary disease using 99mTc-technegas and 99mTc-macroaggregated albumin single-photon emission tomography.

For quantitative evaluation of the regional lung function in patients with interstitial pulmonary disease (IP) in the sitting position, 99mTc-Technegas and 99mTc-macroaggregated albumin (MAA) single-photon emission tomography (SPET) studies were performed in 12 healthy controls (HC) and 42 IP patients. Four transverse images were prepared from the data obtained and designated as slices no. 1-4 from the top downward. Regions of interest (ROIs) were determined in the anterior and posterior parts of the lung in each slice, and the ratio of the count per voxel in the ROIs to the count in the entire lung was calculated as the regional Technegas index (T). The regional perfusion index (Q) was calculated by a similar procedure using the data of 99mTc-MAA SPET. The ratios between T and Q (T/Q) in the anterior and posterior regions of the lung, and the ratios of T and Q between the anterior and posterior regions of the lung (Tp/Ta and Qp/Qa) were examined. In the HC group, T/Q decreased but Tp/Ta and Qp/Qa increased from the upper to the lower lung fields. When IP patients were classified into (I) those in whom T/Q decreased from the upper to the lower lung fields, (II) those in whom it was similar in all slices, (III) those in whom it increased from slice 3 to slice 4, and (IV) those in whom it increased from slice 2 to slices 3 and 4, this classification was more closely correlated with %VC than with %DLCO or PaO2. When the patients were classified according to Tp/Ta and Qp/Qa into (A) those in whom the values were greater in the lower than the upper lung field, (B) those in whom the values were similar in all slices, and (C) those in whom the values were smaller in lower than in upper lung fields, categories B and C were observed frequently even in patients whose %VC was in the normal range. This method is considered to be an effective means to evaluate the progression and pathology of IP and to detect early impairment of lung function.

Adult↗

PubMed1998

Species differences in the disposition of propranolol prodrugs derived from hydrolase activity in intestinal mucosa.

The bioavailability of propranolol (PL) after oral administration of ester-type prodrug was compared in rat and dog, and the possible reason for species difference was investigated. In dog, the oral bioavailability of PL was enhanced by the use of prodrug due to saturation of metabolism of PL. In contrast, high (10 mg/kg) and low (2.5 mg/kg) doses of butyryl PL and isovaleryl PL failed to improve oral bioavailability of PL in rats. The hydrolase activities for prodrugs in rat liver were lower than those of dog (by 4-12-fold), but those of rat intestinal mucosa were significantly higher than those of dog (50-260-fold). Although it is clear from the in vitro hydrolysis using subcellular fractions that the rapid hydrolysis in intestinal mucosa was mainly due to cytosolic components, the brush-border membrane vesicle in rat intestine also showed hydrolase activity for both prodrugs. In situ absorption experiment in rat revealed an improvement in the apparent absorption rate of PL as the result of prodrug use (1.3-fold) and the nearly complete hydrolysis of isovaleryl PL during intestinal absorption, which is a slower hydrolyzed prodrug than butyryl PL in intestinal mucosa and liver. The defects for enhancing oral bioavailability in rats appears to be based on an unsaturation of metabolism for PL, which is derived from a decrease in PL concentration in hepatocytes, owing to rapid hydrolysis of the prodrug in intestinal mucosa and slow hydrolysis of the prodrug in liver. Furthermore, human intestinal mucosa showed a surprisingly high hydrolase activity in microsomes. Therefore, the oral bioavailability of PL after administration of prodrugs might be not significantly improved in human.

Administration, Oral↗

PubMed1998

Effects of absorption enhancers on cytoskeletal actin filaments in Caco-2 cell monolayers.

Histomorphological changes of actin filaments, intracellular levels of calcium ion, and amount of released lactate dehydrogenase (LDH) were examined, in order to elucidate the mechanism of action of three absorption enhancers, i.e., sodium caprate (Cap-Na), sodium deoxycholate (Deo-Na), and dipotassium glycyrrhizinate (Grz-K), using Caco-2 cell monolayers. The structure of actin filaments in microvilli was slightly modified by 0.5 %(w/v) Grz-K and was significantly changed by 0.2 %(w/v) Cap-Na, 0.05 %(w/v) Deo-Na, and 0.0015 %(w/v) ionomycin. All of the enhancers, except Grz-K, induced significantly histomorphological changes in the actin filaments on the middle depth and basal side of the cells. Furthermore, the altered structure of the actin filaments in the monolayers was restored after removal of the Cap-Na, Grz-K and ionomycin, but not Deo-Na. Intracellular levels of calcium ion increased in the following order: ionomycin = Cap-Na > Deo-Na. However, the intracellular calcium ion levels decreased by treatment with Grz-K. The changes in transepithelial electric resistance (TEER) at the initial stage of treatment with all enhancers correlated with intracellular calcium ion levels. These results suggest that one of the mechanisms by which these agents exert absorption-enhancing activity involves structural alterations in the cytoskeletal actin filaments which are provoked by changes in intracellular calcium ion levels. Only the monolayers which were treated with 0.05 %(w/v) Deo-Na released a significant amount of LDH and irreversibly altered the structure of actin filaments, thus indicating that Deo-Na might affect the actin filaments not only by increasing intracellular calcium ion level but also by other, presently unknown factors.

Actins↗

PubMed1998

Mechanical properties and aesthetics of FRP orthodontic wire fabricated by hot drawing.

The FRP wires 0.5 mm in diameter with a multiple fiber structure were fabricated by drawing the fiber polymer complex at 250 degrees C for an esthetic, transparent orthodontic wire. Biocompatible CaO-P2O5-SiO2-Al2O3 (CPSA) glass fibers of 8-20 microm in diameter were oriented unidirectionally in the longitudinal direction in PMMA matrix. The mechanical properties were investigated by 3-point flexural test. The FRP wire showed sufficient strength and a very good elastic recovery after deformation. Young's modulus and the flexural load at deflection 1 mm were nearly independent of the fiber diameter and linearly increased with the fiber fraction. The dependence on fiber fraction obeys well the rule of mixture. This FRP wire could cover the range of strength corresponding to the conventional metal orthodontic wires from Ni-Ti used in the initial stage of orthodontic treatments to Co-Cr used in the final stage by changing the volume ratio of glass fibers with the same external diameter. The estheticity in external appearance was excellent. Thus the new FRP wire can satisfy both mechanical properties necessary for an orthodontic wire and enough estheticity, which was not possible for the conventional metal wire.

Biocompatible Materials↗

PubMed1998

A distamycin A-inducible fragile site, FRA8E, located in the region of the hereditary multiple exostoses gene, is not involved in HPV16 DNA integration and amplification.

The rare fragile site is a specific point on a chromosome that is expressed as an isochromatid gap or break under certain conditions of cell culture and is inherited in a Mendelian codominant fashion. Five folate-sensitive fragile sites were cloned, and the molecular basis of fragile site mutation was shown to be a new class of mutation, called dynamic mutation, resulting from an allelic expansion of (CCG)n repeats. The mechanism responsible for other types of rare fragile sites, i.e., distamycin A-inducible and BrdU-requiring, is unknown, although cytogenetic studies suggested that these fragile sites play a mechanistic role in breakage and recombination and may also be integration and modification sites of foreign viral DNA genomes. A distamycin A-inducible fragile site, FRA8E, is mapped to 8q24.1 in which various loci implicated in genomic instability are located. Here we identified a YAC clone spanning both FRA8E and the hereditary multiple exostosis (EXT1) gene, using fluorescence in situ hybridization (FISH) analysis of a yeast artificial chromosome (YAC) contig. By using P1 clones as probes, the FRA8E locus was further localized to a 400-kb region including the EXT1 gene. Furthermore, the integration and amplification site of human papillomavirus 16 DNA in the ASCC (argyrophil small cell carcinoma) cells were shown not to coincide with FRA8E, but to be involved in an extensively broad genomic region of 8q24.1, including the c-myc gene.

Chromosome Fragile Sites↗

PubMed1998

Correlation between the M and F wave characteristics and the innervated muscle strength in spinal muscular atrophy.

The purpose of this study is to elucidate the interrelation between the M and F wave characteristics of the median nerve and the grip power in patients with spinal muscular atrophy (SMA). The SMA patients showed decreased amplitudes of the M and F waves, decreased frequency of the F wave, and an increase of the F/M ratio as compared with the normative values. The F wave frequency and the amplitudes of M and F waves, which showed a significant linear correlation with each other, became lower in accordance with the decrease of grip power. The properties of M and F waves strongly correlated with the number of surviving motor neurons which would be fewer in those severely affected by SMA.

Adolescent↗

PubMed1998

Preoperative staging of thyroid papillary carcinoma with ultrasonography.

OBJECTIVE: To evaluate the usefulness of ultrasonography including Doppler flow imaging for the preoperative staging of thyroid papillary carcinoma. MATERIALS AND METHODS: In 77 patients with thyroid papillary carcinoma who underwent total thyroidectomy, the accuracy of ultrasonography in preoperative clinical staging was assessed with use of pathologic examination on the basis of TNM classification by the International Union Against Cancer (UICC). RESULTS: In 63 (81.8%) cases, T categories were estimated accurately. The sensitivity in depicting tumor extension into the prethyroidal muscle and/or the sternocleidomastoid muscle was 77.8%, whereas the sensitivity for invasion into the trachea and the esophagus was 42.9 and 28.6%, respectively. In 37 (48.1%) cases, N categories were underestimated, and the sensitivity in the detection of regional lymph node metastasis was 36.7%. Doppler flow imaging was performed in 36 patients, and no correlation was found between flow patterns and the presence of local invasion or regional lymph node metastasis. CONCLUSION: Ultrasonography was useful for preoperative investigation of thyroid papillary carcinoma, but several limitations existed, especially in evaluating extracapsular invasion to deep locations and regional lymph node metastasis.

Adult↗

PubMed1998

Measurement of blood concentration of indocyanine green by pulse dye densitometry--comparison with the conventional spectrophotometric method.

OBJECTIVE: Pulse dye densitometry (PDD) uses two wavelengths (805 and 890 nm) in association with pulse oximetry to compute the arterial blood concentration ratio of indocyanine green (ICG) to hemoglobin (Hb). When Hb is measured in the usual way, this permits the PDD to compute cardiac output, plasma or blood volume, and liver blood flow following an intravenous injection of ICG. In this study, we evaluate the accuracy of the PDD calculation of dye concentration by comparing it with measurement of the dye concentration in blood (Cb) measured by the spectrophotometric cuvette method during dye clearance in patients. METHODS: In 25 patients receiving major abdominal surgery, ICG (10, 20, or 40 mg) was injected into a central vein and arterial ICG concentration was continuously and simultaneously monitored at nose and finger by PDD; concurrently, ICG concentrations were measured by a spectrophotometer at 805 nm in 4 radial arterial blood samples. Repeated measures or one-way ANOVA were used for comparison of ICG concentrations and percent errors by PDD at the nose, finger, and Cb. RESULTS: The percent error (bias) of calculated dye concentration and its standard deviation (precision) was -3.9 +/- 16.8% (p < 0.01) with the probe on a nostril and 3.4 +/- 12.6% using the finger probe. These errors were found to be greatest when the mean transit time of the dye was rapid (-20.7 +/- 6.8% at nose p < 0.01 and -8.5 +/- 2.5% at finger p < 0.05) due to factors other than the time delay of blood sampling. CONCLUSION: These errors are of similar size to those associated with thermal cardiac output measurement, suggesting that PDD should be valuable clinically as a noninvasive tool especially since it provides values for blood volume and liver blood flow.

Aged↗

PubMed1998

Species differences in stereoselective hydrolase activity in intestinal mucosa.

PURPOSE: The aim of this study is to investigate species differences in the stereoselective hydrolysis for propranolol ester prodrugs in mammalian intestinal mucosa and Caco-2 cells. METHODS: Hydrolase activities for propranolol prodrugs and p-nitrophenylacetate in man (age: 51-71 years), the beagle dog (age: 4 years) and Wistar rat (age: 8 weeks) intestinal mucosa, and also in Caco-2 cells (passage between 60-70) were estimated by determining the rate of production of proparanolol and p-nitrophenol, respectively. RESULTS: The hydrolase activities for both propranolol prodrugs and p-nitrophenylacetate were in the order of man > rat >> Caco-2 cells > dog for intestinal microsomes, and rat > Caco-2 cells = man > dog for intestinal cytosol. Dog microsomes showed stereoselective hydrolysis for propranolol prodrugs, but not those from human or rat. Interestingly, both subcellular fractions of Caco-2 cells showed remarkable R-enantioselectivity except acetyl propranolol. Enzyme kinetic experiments for each enantiomer of butyryl propranolol in microsomes revealed that dog possesses both low and high affinity hydrolases. Both Km and Vmax values in rat were largest among examined microsomes, while Vmax/Km was largest in man. Finally, it was shown that the carboxylesterases might contribute to the hydrolysis of propranolol prodrug in all species by inhibition experiments. CONCLUSIONS: The hydrolase activities for propranolol prodrugs and p-nitrophenylacetate in intestinal mucosa showed great species differences and those in human intestine were closer to those of rat intestine than dog intestine or Caco-2 cells.

Aged↗