Interaction between phenytoin and enteral nutrients and its influence on gastrointestinal absorption.

The gastrointestinal absorption of phenytoin (PHT), an antiepileptic drug, is often affected by its interaction with co-administered enteral nutrients through a nasogastric (NG) tube, resulting in decreased plasma PHT concentration. In this study, we measured the recovery rate (%) of PHT (Aleviatin® powder) passed through an NG tube when co-administered with distilled water or enteral nutrients (F2α®, Racol® NF, Ensure Liquid® and Renalen® LP). We also measured plasma PHT levels in rats, after oral co-administration of PHT with enteral nutrients. We demonstrate that PHT recovery rate was close to 100 % in all cases after passage through the NG tube. In the rat study, the AUC0→∞ of PHT concentration after oral administration significantly decreased when it was co-administered with F2α® and Racol® NF compared to distilled water. However, the AUC0→∞ of PHT was unchanged when co-administered with F2α® 2 h after initial PHT administration. We therefore conclude that the co-administration of PHT with F2α® and Racol® NF caused a reduction in the absorption of PHT from the gastrointestinal tract to the blood, without adsorption to the NG tube. The administration of enteral nutrients 2 h after PHT is one clear way to prevent a decrease in plasma PHT concentration.

Effects of Gosha-jinki-gan (Chinese herbal medicine: Niu-Che-Sen-Qi-Wan) on hyperinsulinemia and hypertriglyceridemia in prediabetic Zucker fatty rats.

The Chinese herbal medicine, Goshajinki-gan (GJ) (Niu-Che-Sen-Qi-Wan), has been widely used for treating patients with melalgia, lower back pain, numbness, and diabetic neuropathy. We investigated the effects of GJ on the regulation of serum insulin and triglyceride levels in obese Zucker fatty rats (fa/fa; ZFR). We administrated GJ to 6-week-old ZFR and non-obese lean rats (LR) for 12 weeks. Body weight and serum glucose, insulin, total cholesterol, and triglyceride levels were significantly increased at 18 weeks in ZFR as compared to the LR. GJ treatment in ZFR significantly suppressed elevation in serum glucose, insulin, and triglyceride levels, but no significant differences were observed in body weight and serum cholesterol levels in the ZFR group with GJ treatment compared to the ZFR group without GJ treatment. These results suggest that GJ may improve hyperinsulinemia and hypertriglyceridemia in ZFR and that GJ may be useful for preventing or delaying the onset of diabetes mellitus in a pre-diabetic state.

Efflux transporter mRNA expression profiles in differentiating JEG-3 human choriocarcinoma cells as a placental transport model.

The kinetics of drug transport across the trophoblast layer is determined by several factors. Human choriocarcinoma cell lines like BeWo and JEG-3 have been used as models of the trophoblast layer to examine the placental transport of drugs. Previously, the drugs examined in these models have been readily transported across the trophoblast layer via cellular gap junctions. These backgrounds enabled us to establish the differentiating JEG-3 cell (DJEG) layer model, which suppresses paracellular drug transport, as an evaluation system of placental drug transport. The efflux transporters on the trophoblast layer assume the meaningful role of protecting the fetus from xenobiotic substances. In order to clarify the usefulness of our DJEG placental drug transport model, this study examined the mRNA expression profiles of the efflux transporters MRPs, MDR1, and BCRP in JEG-3 cells and compared them with those of BeWo cells and their known placental expression. We suggest that the mRNA of efflux transporters MRP 1-8 and BCRP are expressed widely in JEG-3 cells; however, expression levels of MDR1 mRNA were undetectable. It was also indicated that polymorphisms of BCRP C421A in both the BeWo and JEG-3 cells are of the wild-type. We demonstrated the efflux transporters' expression profiles, as well as those of the BeWo cells, was demonstrated in the DJEG placental drug transport evaluating model as well as the BeWo cells, in the DJEG placental drug transport evaluation model. Based on these findings, we hope that the DJEG model will be adequate for use in evaluating placental drug transport in relation to the transporter proteins.

Effects of Gosha-jinki-gan (Chinese herbal medicine: Niu-Che-Sen-Qi-Wan) on hyperinsulinemia induced in rats fed a sucrose-rich diet.

We investigated the effects of a Chinese herbal medicine, Gosha-jinki-gan (GJG), on the regulation of insulin levels in rats fed a sucrose-rich diet (SRD). Normal Wistar rats in the SRD group were fed an SRD for 4 weeks. Increased dietary sucrose did not alter plasma glucose levels but it increased plasma insulin levels at 2 and 4 weeks in the SRD-fed rats relative to control rats that were fed standard chow. GJG treatment significantly suppressed the SRD-induced elevation in plasma insulin levels. These results suggest that GJG improves hyperinsulinemia caused by an SRD.

Effects of the herbal medicine Hachimi-jio-gan (Ba-Wei-Di-Huang-Wan) on insulin secretion and glucose tolerance in type 2 diabetic Goto-Kakizaki rats.

Hachimi-jio-gan (HJ) is a Chinese medicine that has been widely used for the treatment of nephrotic syndromes, hypertension, and diabetes mellitus. We reported that HJ lowers plasma glucose in type 1 diabetic rats. We investigated the effects of HJ on diabetic hyperglycemia and insulin secretion in type 2 diabetic Goto-Kakizaki (GK) rats. Eight-week-old diabetic GK rats were given free access to pellets containing 1% HJ extract powder for 14 weeks. HJ consumption increased the food intake and body weight of these rats in comparison to control rats. HJ may control the body weight loss observed in GK rats. HJ also reduced hyperglycemia in diabetic GK rats, and it significantly increased insulin secretion in non-fasting GK rats over the experimental period. In oral glucose tolerance tests, HJ significantly improved the insulin response at 30 min and reduced the plasma glucose level at 60 min after glucose administration (p < 0.05). Ten weeks after administration, the plasma leptin levels significantly increased in the HJ group rats. These results demonstrate that in diabetic GK rats, HJ decreased the level of postprandial glucose via enhanced insulin secretion coupled with the regulation of food intake by leptin.

Characterization of multidrug resistance-associated protein mRNAs expression profiles in Caco-2 and HT-1080 cell lines induced by methotrexate.

An efflux function induced by multidrug resistance-associated proteins (MRPs) contributes to the mechanisms of resistance to methotrexate (MTX). Since it has been reported that the human Caucasian colon adenocarcinoma cell line (Caco-2) shows high MRPs expression, it is assumed that Caco-2 cells are resistant to MTX. Alternatively, the human fibrosarcoma cell line (HT-1080) has been reported to be highly sensitive to MTX. In this study, the difference in the growth-inhibitory activity of MTX in these cell lines was compared as a characteristic of sensitivity. Subsequently, the characterization of MRP (1-8) mRNAs expression profiles before and after MTX exposure in these cell types was examined with the multiplex reverse-transcription-polymerase chain reaction (RT-PCR) method. It was demonstrated that the expressions of MRP2, MRP3, MRP6, and MRP8 mRNAs in the HT-1080 cells were lower than those in the Caco-2 cells and that only MRP5 mRNA expression was induced in the Caco-2 cells after MTX treatment. The MRP mRNAs expression profiles between these two cell lines could be differentiated widely. The characterization of MRPs profiles might be associated with resistance to MTX in cells. Additionally, this multiplex RT-PCR method would be beneficial for further time-dependence investigations of the MRP mRNAs expression profiles.

Localization of glucagon-like peptide-2 receptor mRNA expression at different sites in the small intestine of rats.

Preproglucagon is known to be processed into glucagon-like peptide (GLP)-1, GLP-2, and glicentin in the L cells of the intestinal tract. GLP-2 has been shown to possess intestinotrophic activity in rodents. However, the ligand-binding mechanisms of GLP-2 receptor (GLP-2R) have not been extensively investigated. The present study sought to determine the localization of GLP-2R in the small intestine by analyzing GLP-2R mRNA expression using the reverse transcriptase-polymerase chain reaction (RT-PCR) method. GLP-2R mRNA expression was detected at all sites in the small intestine; its expression levels were particularly high in the jejunum. Moreover, GLP-2R mRNA expression was detected in both non-mucosal intestinal tissues and intestinal mucosa. These findings suggest that in addition to the intestinal mucosa, the functional sites of GLP-2 may be present in the non-mucosal tissues. These results imply that GLP-2 peptide acts as an intestinotrophic factor that may affect the intestines from outside the mucosa. The intestinotrophic effect of GLP-2 from outside the mucosa may be a function of the enteric neurons transmitting several growth signals to mucosal cells.

Enhancing effect of N-dodecyl-2-pyrrolidone on the percutaneous absorption of 5-fluorouracil derivatives.

The enhancing effects of N-dodecyl-2-pyrrolidone (NDP) on the percutaneous absorption of doxifluridine (DOX), 5-fluorouracil (5-FU), tegafur (TEG) and carmofur (CAR) were examined using an in vitro penetration technique and rat skin. Phosphate buffered isotonic saline (PBS), propylene glycol (PG) and PG containing 0.4M NDP (PGNDP) were applied as the donor solution. The correlation between the n-octanol/water partition coefficients and the permeability coefficients of DOX, 5-FU and TEG was investigated using both logarithmic plots. It was determined that the permeability coefficients are significantly correlated with their n-octanol/water partition coefficients on PBS. This result suggested that the non-polar stratum corneum lipid lamella in the skin might act as a rate limiting step on the skin penetration of DOX, 5-FU and TEG. The permeability coefficient of DOX, 5-FU and TEG was increased on PGNDP. The enhancing effect of NDP on the permeability coefficient was more effective at higher hydrophilic drugs, the values of the permeability coefficient had almost the same values on PGNDP and the dependency of the permeability coefficient on the n-octanol/water partition coefficient disappeared in the presence of NDP. These results indicated that the enhancing effect of NDP on the percutaneous absorption of DOX, 5-FU and TEG might be closely related to the perturbation of stratum corneum lipid lamella. Since it has been well recognized that CAR is decomposed into 5-FU in neutral and alkaline solution, the decomposition rate of CAR was measured using PBS solution and was found to be very rapid (Kd = 3.17 h-1, t1/2 = 13.1 min). The total concentrations of CAR plus 5-FU in the acceptor compartment were used to determine the permeability coefficient of CAR. The obtained value of the permeability coefficient of CAR on PG was almost the same as that of TEG on PG (CAR: 1.11 x 10(-3) cm/h, TEG: 1.24 x 10(-3) cm/h), while that of CAR on PGNDP was smaller than that of TEG on PGNDP (CAR: 6.06 x 10(-3) cm/h, TEG: 1.24 x 10(-2) cm/h). To determine the lipophilic property of CAR, the lipophilic index (log k') was measured by HPLC. The value of the lipophilic index of CAR was 92 times higher than that of TEG. These results indicated that CAR is a higher lipophilic compound, and the smaller value of the permeability coefficient of CAR compared with that of TEG on PGNDP might be caused by the strong binding of CAR to the rat skin (dermis). The dermis might act as a rate limiting step on the skin penetration of CAR, and the percutaneous absorption of CAR might be controlled by both the stratum corneum and the dermis.