Pentosidine, a fluorescent cross-linking compound, accumulates in extracellular matrix, espcially in the collagen, and is formed by the nonenzymatic process of advanced Maillard reaction. We developed a method of determination of pentosidine and tried to examine its level in urine and serum of elder patients. The method, which involves the hydrolysis of samples, pretreatment using a CF-11 cellulose column and HPLC quantification, resulted in a high recovery (94.3%) of pentosidine with low coefficient of variation (8-10%) of total analysis. Serum and urinary levels of pentosidine in control subjects gradually increased with age. Elder patients with cerebral infarction showed higher levels of serum and urinary pentosidine as compared with those with senile dementia and other geriatric disorders. These results suggest that serious damage to systemic vascular tissues has already occurred in these patients due to glycation.
The effect of dexamethasone (Dex) pretreatment on the Dex-dependent induction of tyrosine aminotransferase (TAT) activity was studied in primary cultured rat hepatocytes. The extent of the Dex-dependent induction of TAT activity decreased during culture in untreated cells. Dex pretreatment prevented this decrease. A Scatchard plot analysis of the results of a [3H]Dex binding assay showed that hepatocytes cultured for 2.5 h possessed both high and low affinity binding sites in their cytosols. The number of both high and low affinity binding sites decreased during culture for a further 24 h in untreated cells. Dex pretreatment partly prevented the decrease in low affinity binding sites but had no effect on the decrease in high affinity binding sites. These results show that Dex pretreatment counteracts the usual decrease in the inducibility of TAT activity, and suggest that this action of Dex may be due to the maintenance of low affinity binding sites. These results also suggest that low affinity binding sites could possibly mediate the biological response to Dex.
The mechanism of the killing and cytocidal effects produced by HYI toxin from Williopsis saturnus var. saturnus, and by amphiphilic antibiotics aculeacin A and papulacandin B on yeast Saccharomyces bayanus cells was studied. When the yeast cells were treated with these molecules, a discharge of cell materials at the budding position was observed by phase-contrast and scanning electron microscopy. The cytocidal effect of these molecules was most pronounced when the cells were in the logarithmic growth phase. Washing the HYI toxin incubation mixture completely eliminated the killing activity, but in the case of the antibiotics, it only partially reduced the cytocidal activity. Full recovery of the killing activity in the supernatant of the washing solution was observed after XYI toxin incubation, but in the case of the antibiotics, the recovery of cytocidal activity was time-dependent. The activity of membrane β-1, 3-glucan synthase was potently inhibited by HXI toxin, and the concentration of this enzyme in the budding tip was observed. These results suggest that HYI toxin exerts a cytocidal effect on the budding of sensitive yeast cells by inhibiting cell wall synthesis. This mechanism is similar to that of the HM-1 toxin of W. saturnus var. mrakii, and to aculeacin A and papulacandin B, although there are some differences from that of HYI toxin.
Thymidylate synthase (TS) catalyzes the conversion of deoxyuridylate to thymidylate. Promoter regions of the TS gene from three vertebrates, human, mouse and rat, have been analyzed so far. A unique inverted repeat was present in the promoter region of the human, but not in the mouse and rat, TS genes, and the feature of the promoter region is considerably different between the human TS gene and the two rodent TS genes. To examine whether the characteristics of the human TS gene promoter is intrinsic to human or primate, we cloned a DNA fragment containing the promoter region of the monkey TS gene and determined the nucleotide sequence in this region. The nucleotide sequence in the promoter region of the moneky TS gene was revealed to have 88% homology with that in the corresponding region of the human TS gene. The unique repeted structure mentioned above was also found in the monkey TS gene. Furthermore, the Sp1-binding motif and the CACCC box were found to be conserved in the monkey TS gene. The result of chloramphenicol acetyltransferase assay suggested that the Sp1-binding motif and the CACCC box are essential for the promoter activity of the monkey TS gene, as in the case of the human TS gene.
In the trophoblast layer of the chorion laeve of human fetal membranes obtaiend by cesarean section at the month of normal parturition, cells with condensed nuclei could be observed by histochemical examination. Incubating fetal membranes at 37°C in vitro in cultivation medium, the frequency of cells with condensed nuclei increased in the chorion laeve, associating with an increase in DNA fragmentation and the population of in situ TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-X nick end labeling) staining-positive cells. The progressed apoptotic cell death in the chorion laeve in vitro was suppressed by incubation of the tissue in the presence of glucocorticoids, cortisone or hydrocortisone, which was also demonstrated by DNA fragmentation analysis and in situ TUNEL staining. These results reveal that a substantial proportion of trophoblast cells in the chorion laeve of human fetal membranes are induced to undergo apoptosis at the end of pregnancy, and that the apoptosis progresses rapidly in vitro as the incubation period increases. It is suggested that certain hormones such as glucocorticoid, may be related to the regulation of the apoptosis in human fetal membranes.
Herbimycin A is widely used as an inhibitor of Src family protein tyrosine kinases but is also reported to induce the downregulation of epidermal growth factor (EGF) receptor number in A431 cells without inhibiting its tyrosine kinase activity. To determine the specificity of the receptor downregulation, we examined its effect on a variety of cell lines which express different levels of EGF receptor and on other tyrosine kinase receptors. Longterm herbimycin A treatment decreased the amounts of all the tyrosine kinase receptors examined in a dose-dependent manner. It also reduced ligand-stimulated receptor autophosphorylation in accordance with the reduction in the receptor level. Herbimycin A inhibited platelet derived growth factor (PDGF)-induced tyrosine phosphorylation of cellular proteins and DNA synthesis in NIH3T3 cells but did not affect the serum-stimulated DNA synthesis. PDGF-induced tyrosine phosphorylation and activation of c-Src was inhibited but the protein level of c-Src was not reduced by herbimycin A. The reduced level of c-Src kinase activity correlated with the levels of both PDGF receptor and DNA synthesis. These results indicate that the herbimycin A treatment selectively downregulates receptor tyrosine kinases, independent of the number of receptors, and suggest that c-Src is to some degree involved in the selective inhibition of PDGF-induced mitogenesis by herbimycin A.
Glycyrrhizin (GL) was hydrolyzed to glycyrrhetic acid (GA), glycyrrhetic acid mono-β-D-glucuronide (GAMG) or both by glucuronidases in various organs of rat. GL β-D-glucuronidase I, hydrolyzing GL to GA; GAMG β-D-glucuronidase, hydrolyzing GAMG to GA; and 3α-hydroxyglycyrrhetinate (3α-hydroxyGA) dehydrogenase, oxidizing 3α-hydroxyGA to 3-oxo-GA were found in the organs of this animal. GL β-D-glucuronidase II was distributed in the lysosomal fraction of all organs except brain; 3α-hydroxyGA dehydrogenase was distributed in the microsomal fraction of the liver; but other enzymes were distributed in the nuclear, lysosomal, microsomal and soluble fractions of a variety of organs. GL β-D-glucuronidase I, GL β-D-glucuronidase II and GAMG β-D-glucuronidase activities in a mixture of lysosomes and microsomes of rat liver exhibited different patterns on hydroxyapatite column chromatography. These results showed the metabolic pathways of GL to be of two types : a β-D-glucuronidase hydrolyzing GL to GA, and the other consisting of two different β-D-glucuronidases hydrolyzing GL to GAMG and GAMG to GA.
This study examines the effects of protein kinase inhibitors and activator on angiotensin II-induced DNA synthesis and protein synthesis of rat aortic smooth muscle cells. In quiescent confluent cells, angiotensin II induced a concentration-dependent increase in thymidine incorporation and leucine incorporation. The tyrosine kinase inhibitor genistein caused an inhibition of the angiotensin II-induced DNA synthesis but not of the agent-induced protein synthesis. The protein kinase C inhibitors staurosporine and calphostin C caused an inhibition of the angiotensin II-induced protein synthesis but not of the agent-induced DNA synthesis. The potein kinase C activator phorbol 12-myristate 13-acetate stimulated protein synthesis. Angiotensin II stimulated mitogen-activated protein (MAP) kinases and the angiotensin II-induced MAP kinase activation was inhibited by genistein but not by staurosporine. These findings suggest that angiotensin II-induced DNA synthesis is at least partly mediated via protein-tyrosine phosphorylation and angiotensin II-induced protein synthesis is at least partly mediated by activation of protein kinase C. It seems likely that MAP kinase activation is involved in DNA synthesis but not in protein synthesis induced by angiotensin II.
Mice, at weaning, were placed on a diet supplemented with beef tallow (BT), linoleic acid (18 : 2n-6)-rich saffower oil (SO), α-linolenic acid (18 : 3n-3)-rich perilla oil (PO) or docosahexaenoic acid (22 : 6n-3, DHA)-rich fish oil (FO) to modify membrane fatty acid vulnerability to peroxidation, then carbon tetrachloride (CCl4) was administered chronically. CCl4-induced liver injury, estimated using serum alanine aminotransferase activity and liver hydroxyproline content, was not different among the 4 dietary groups; however, the FO diet lowered the liver triacylglycerol (TG) level when compared with the BT and SO diets. The FO diet group exhibited a significantly higher level of thiobarbituric acid-reactive substances (TBARS) in the liver when compared with the three other dietary groups. Chronic CCl4 treatment decreased the proportion of eicosanoid precursors (arachidonate and eicosapentaenoate) rather than that of DHA, with the highest peroxidizability among major fatty acids in liver, and did not enhance TBARS formation in any of the dietary groups. The protein carbonyl content in the liver was similar among the 4 dietary groups but was decreased following CCl4 treatment. Liver α-tocopherol contents were affected both by diet and CCl4 treatment, and a positive correlation was observed between α-tocopherol and TG contents. These results indicate that increasing the autoxidizability of dietary fatty acids or the chronic CCl4 treatment did not synergistically enhance liver injury or the accumulation of oxidation products in mice.
Bactericidal action of novel bis-quaternay ammonium compounds (bis-QACs), 4, 4'-(α, ω-polymethylenedithio)bis(1-alkylpyridinium iodide)s (4DTBP-m, n) was studied. The bactericidal activity of 4DTBP-m, n in water was not affected by the molecular hydrophobicity unlike general mono-QAC, N-dodecylpyridinium iodide (P-12), while the bacteriostatic activity in the medium was reduced with their hydrophobicity. This result suggested that the hydrophobic materials in the medium interact with 4DTBP-m, n and cover their active moiety. Since the bactericidal activity using the measurement system supplemented with peptone was influenced by the molecular hydrophobicity, this speculation was supported. The plots of the bacteriostatic activities of 4DTBP-m, n against the surface hydrophobicities of various bacteria accord to the straight line as in the case of P-12. The slope of the line of 4DTBP-6, 12 was comparatively smaller than that of 4DTBP-6, 8, indicating that the compounds having longer alkyl group tend to reduce their activities against the bacteria with hydrophobic cell surface because of their interaction with the hydrophobic materials. The novel bis-QACs have an ability to liberate rapidly and abundantly the turbid materials from cells, that is, a bacterioclastic activity. The bacterioclastic activity of P-n was influenced by the length of alkyl group, while 4DTBP-6, n had almost the same activity regardless of its length. Observation by scanning electron microscope (SEM) revealed that 4DTBP-6, 8 fatally damaged Escherichia coli cells, and that the morphological alteration of the cells caused by the bis-QAC was greatly different from that of the usual QAC. Therefore, the effective bacterioclastic action, and excellent bactericidal action is due to the unique dimeric structure of 4DTBP-m, n.
We investigated the effect of components in grapefuit juice (GFJ) on the transport of vinblastine, a substrate of P-glycoprotein (P-gp), across Caco-2 cells. The apical to basolateral flux of [3H]vinblastine was increased in the presence of GFJ extracts. The steady-state uptake of [3H]vinblastine from the apical side was significantly increased in the prsence of GFJ in a dose-dependent manner within the range of 2.5 to 50% (v/v) of GFJ. Although naringin and naringenin reduced apial efflux of [3H]vinblastine at the concentration prenset in GFJ and increased steady-state uptake from the apical side to 124 to 240%, respectively, the observed effect of naringin was not enough to account for the effect of GFJ and naringenin is not naturally present in GFJ. To investigate the effective components in GFJ, we examined the inhibitory effect of several organic solvent extracts of GFJ on the transport of [3H]vinblastine in Caco-2 cells. Organic solvent extracts of GFJ enhanced the apical to basolateral transcellular transport and inhibited the apical efflux. The permeability coefficient of apical to basolateral transport of [3H]vinblastine increased in the order of the ethyl acetate>diethyl ether>methylene chloride extracts of GFJ. Since the extracted amount of naringenin by ethyl acetate was less than that with the other organic solvents, the primary inhibitor in GFJ is suggested to be different from this flavonoid. The present study demonstated the existence of inhibitory components in GFJ for the P-gp function in Caco-2 cells, which are distinct from known components such as naringin or naringenin.
Glial cells are able to support neurons physically and functionally. The present study was undertaken to determine the effects of Kampo medicines on glial cell function, especially Ca<2+> mobilization. C6 rat glioma cells expressed H1-histamine, muscarinic cholinergic and adrenergic α1-receptors, simulation of which resulted in phosphoinositive hydrolysis and increase in intracellular Ca<2+> concentration ([Ca<2+>]i).The water extracts of Sho-saiko-to and San'o-shashin-to, Kampo medicines which contain Scutellariae Radix (Ogon, the root of Scutellaria baicalensis GEORI), inhibited histamine (100μM)-induced increase in [Ca<2+>]i in a concentration-dependent manner. The water extract of Scutellariae Radix potently decreased [Ca<2+>]i in a concentration-dependent manner. Sho-saiko-to, San'o-shashin-to and Scutellariae Radix significantly inhibited histamine-induced accumulation of total [3H]inositol phosphates, consistent with their inbition of the increase in [Ca<2+>]i. These results suggest that Sho-saiko-to, San'o-shashin-to and Scutellariae Radix inhibit Ca<2+> mobilization mediated via an inhibition of phospholipase C. The inhibitory effect may be important in interpreting the pharmacological actions of above Kampo medicines.
Inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice was observed in the methanol extract of rice bran and γ-oryzanol. The active components of rice bran, sitosterol ferulate, 24-methylcholesterol ferulate, cycloartenol ferulate and 24-methylenecycloartanol ferulate inhibited markedly the TPA-induced inflammation in mice. The 50% inhibitory does of these compounds for TPA-induced inflammation was 0.2-0.3 mg/ear. Furthermore, cycloartenol ferulate markedly inhibited the tumor-promoting effect of TPA in 7, 12-dimethylbenz[a]anthracene-initiated mice.
As part of the search for anticomplemertary active components from natural products, the anticomplementary properties of methanolic extracts from the flower buds of Magnolia fargesii have been investigated. Bioassayguided chromatographic separation of the active consituents led to the isolation of compound 1, whose structure was identified by spectroscopic methods to be kaempferol 3-O-β-D-(6"-O-coumaroyl)glucopyranoside (tiliroside). Tiliroside showed very potent anti-complement activity (IC50=5.4×10-5 M) on the classical pathway of the complement system, even higher than rosmarinic acid, which is a well-known inhibitor against the complement system. On the other hand, the hydrolysates of tiliroside, kaempferol, astragalin and p-coumaric acid showed very weak activity on this system.
The Kampo medicine Shichimotsu-koka-to (SKT) is used to treat hypertension and atherosclerosis in Japan. The action of SKT was studied, focusing on nitric oxide, which is intimately involved in regulation of blood pressure and cell functions associated with atherogenesis and inflammation. Oral administration of SKT enhanced serum nitric oxide (NOx) levels does-dependently and 3 d administration was enough to detect its effect. The maximal level of serum NOx was maintained at around 27 μM, a concentration which did not result inharmful effects on cells. On the other hand, L-arginine, the substrate of NO synthase (NOS), was also increased by SKT administration. When the source of L-arginine was studied, only 12.7 mg of L-arginine was contained in 1 g of SKT and this amount of L-arginine could not explain the increased L-arginine levls in serum. These results suggest taht SKT may enhance serum L-arginine by acting on L-arginine metabolism, but not supplying L-arginine itself, resulting in enhancement of serum NOx. In conclusion, the antihypertensive and antiatherosclerotic action shown by SKT may be in part due to enhanced serum NOx, thus suggesting that SKT may become a unique orally active drug for cardiovascular diseases as a new NO donor.
To improve the absorbability of phenytoin (DPH), a prodrug, N-acetyl-DPH (EDPH), was synthesized, and the absorptive characteristics and pharmacokinetics of the prodrug were evaluated in rats. EDPH was rapidly hydrolyzed to DPH in the intestinal fluid and the mucosa (rate constant, 0.055 and 0.169 min-1, respectively). The plasma concentrations of DPH after intravenous dosing of EDPH declined in a biexponential manner, although two different elimination patterns were observed in these rats. When dosed orally (25 mg/kg, DPH equivalent), the plasma levels of DPH converted from the prodrug were significantly higher and more sustained than those after DPH alone, giving bioavailability 11.4 (rapid decay) and 9.1 times (slow decay) as high, respectively, as that after DPH alone. The concentrations of DPH distributed into the mucosa of the duodenum and jejunum 1 and 5 h after oral dosing of EDPH were significantly higher than those after DPH alone. The prodrug and DPH converted from the prodrug dissolved 2-4 fold more than DPH alone in bile salt solution and bile salt-oleic acid mixed micelles, indicating the increased solubility of the prodrug in the intestinal fluid. It is concluded from the data that such high solubility of EDPH enhanced the intestinal absorption of the prodrug, part of which would be absorbed in the amide form, and thus gave the high bioavailability.
Extracellular-superoxide dismutase [EC 18.104.22.168] (EC-SOD) is a secretory glycoprotein with high affinity for heparin. This enzyme locates in blood vessel walls at a high enough level to suppress oxidative stress under normal conditions. EC-SOD is the major SOD isozyme in plasma, anchored to heparan sulfate proteoglycans in the glycocalyx of endothelial cell surfaces. Plasma EC-SOD is heterogeneous in heparin affinity and can be divided into five fractions, I to V, by heparin-HPLC. It has been suggested that EC-SOD form V is the primacy form synthesized in the body and that EC-SOD forms with reduced heparin affinity are the result of proteolytic truncation of the C-terminal end of EC-SOD form V which is responsible for the binding with heparin. Recently, we reported that only plasma EC-SOD form V, with the highest heparin affinity, was incresed by intravenous injection of heparin. The heparin affinity of plasma EC-SOD in patients with coronary atherosclerosis (CA+ patients) was compared in this study. The increase of plasma EC-SOD from V after heparin injection in CA+ patients was significantly less than that in subjects without evidence of stenosis in their major coronary arteries (CA- subjects). On the other hand, in CA+ patients, EC-SOD forms I to III, with low heparin affinity, were significantly increased compared to those in CA- subjects. EC-SOD in plasma apparently forms an equilibrium between the plasma phase and endothelial cell surface, and EC-SOD on the endothelial cell surface contributes to protecting the vessel wall against oxidative stress. The findings suggest that the quantitative and qualitative changes of EC-SOD, i.e., the decrease of bound EC-SOD on the endothelial cell surface, might suppress the defense systems against oxidative stress, which causes in part the development of coronary artery atherosclerosis.
Transcription factor Sp1 is a Cys2His2-type zinc finger protein that specifically binds to GC-boxes on numerous viral and cellular genes. In this study, we prepared several Sp1 mutant peptides Sp1 (530-696) containing zinc finger region and the domain D, and Sp1 (530-623) containing only zinc finger region, and then investigated the participation of the C-terminal domain D of Sp1 for GC-box binding. Gel mobility shift assays demonstrate that Sp1 (530-696) evidently shows DNA-binding modes different from Sp1 (530-623) and that the Sp1 mutant containing the domain D self-interacts directly. Domain D may play an important role in the synergistic activation of Sp1 by the stacking of tetramers. A novel model for Sp1 oligomerization has also been proposed.
A cytotoxic factor (CF) toward cultured murine leukemia L1210 cells was induced in mouse serum by intravenous injection of a dehydrogenation polymer of p-coumaric acid (DHP-pCA). When the serum from the treated mice was diluted with ethanol, CF was preserved in its supernatant (EtOH-sup). An EtOH-sup prepared from untreated control mice also showed cytotoxicity, although at much higher concentrations. The CF activity of EtOH-sups from both treated and untreated mice was completely eliminated by acid treatment at pH 2 at 90°C for 30 min but kept intact by alkali treatment. In addition, the CF activity of both EtOH-sups was not affected by digestion with chymotrypsin. CF was recovered in a neutral MeOH-eluate from a DEAE-cellulofine column but not in HCl-MeOH eluate, in which lignified materials including DHP-pCA should have been recovered. These findings strongly suggest that CF is not a metabolite of DHP-pCA but an endogenous component of the normal serum which is augmented by DHP-pCA administration.
The structure-activity relationships of lipopolysaccharide (LPS) in tumor necrosis factor-α (TNF-α) production and induction of macrophage cell death in the presence of cycloheximide (CHX) were examined in a murine macrophage-like cell line, J774.1. TNF-α production is one of the characteristic phenotypes of LPS-activated macrophages, and is observed upon incubation with LPS. On the contrary, macrophage cell death, which had been found in our laboratory (Amano F., Karahashi H., J. Endotoxin Res., 3, 415-423 (1996)) and was examined as the release of lactate dehydrogenase (LDH) from cells into the culture supernatant, was observed 2.5 h after the addition of LPS in the presence of CHX. However, both TNF-α production and macrophage cell death were similarly dependent on the structures of LPS and lipid A. At more than 10 ng/ml, wild-type LPS from E.coli and S. minnesota exhibited the highest activity, and LPS as well as diphosphoryl lipid A from S. minnesota rough mutants also exhibited activity, but E. coli LPS detoxified by alkaline treatment or monophosphoryl lipid A from S. minnesota exhibited no activity even at 100 ng/ml. These results suggest that LPS-induced macrophage cell death in the presence of CHX shows similar requirements for LPS and/or lipid A structures as for the macrophage activation at higher doses than 10 ng/ml, although the former was not observed at 1 ng/ml LPS, while the latter was. However, TNF-α does not seem to be involved in the induction of macrophage cell death, because a neutralizing anti-TNF-α antibody failed to block the macrophage cell death and because recombinant TNF-α had little effect on the extent of LDH release in the presence or absence of LPS and/or CHX, and also because TNF-αproduction by LPS was abolished in the presence of CHX.
The mature form of rat adrenodoxin (Ad) was purified from a heterologous direct expression system in Es-cherichia coli with a yield of 56 mg/l culture. The purified Ad showed a A414/A280 ratio of 0.91 and the sequence of 10 amino terminal residues was identical with that of authentic rat Ad. By Time of Flight/Mass spectrometry, the molecular mass of purified Ad was identical to that calculated from the cDNA sequence and the carboxy terminal residue was estimated to be Ser, which was also as expected from the cDNA. These results indicate that the purified recombinant Ad is a precise mature form. In measurements of NADPH-cytochrome c reductase activity reconstituted which bovine adrenodoxin reductase (AdR), the apparent Km value for rat Ad was 46.9±2.5 nM, indicating a somewhat lower affinity for rat Ad to bovine AdR than for bovine Ad. On the other hand, the spectral Kd value for rat Ad to bovine cytochrome P-450scc was 0.46±0.05 μM, a value which was almost identical with that of the bovine counterpart.
Many plant polysaccharide fractions have been reported as immunomodulatory agents. However, sometimes the possibility of contamination with bacterial lipopolysaccharide (LPS), a potent B cell mitogen and immune modulator, is discussed. In the present paper, we investigated the effects of crude polysaccharide fractions obtained from the shoot and hairy root of Glycyrrhizae sp. on murine peritoneal macrophage function, in order to clarify whether plants grown under aseptic conditions produce immunomodulatory polysaccharides. All crude polysaccharide fractions induced nitric oxide production by murine peritoneal macrophages in vitro. Chemical analysis revealed that LPS-like molecules were not present in all preparations. These results suggested that shoot and hairy root biosynthesized polysaccharides that could stimulate macrophages de novo.
In this study, the transcellular transport characteristics of four β-lactam antibiotics (cefotaxime, cefmenoxime, cefmetazole, and cefotiam) were investigated in a kidney epithelial cell line LLC-PK1, especially focusing on the effect of the N-methyl-tetrazole-thiol (NMTT) group attached to 7-amino-cephalosporanic acid. There were no directional differences between the apical-to-basolateral and basolateral-to-apical transport of cefotaxime, cefmenoxime, and cefmetazole, suggesting that the NMTT group does not influende the transcellular transport behaviors of β-lactam antibiotics. In contrast, cefotiam transport across LLC-PK1 cell monolayers was 1.3-fold greater in the basolateral-to-apical direction than in the apical-to-basolateral direction. It is considered that the ionization of nitrogen in the N-dimethylaminoethyl group attached to NMTT is a factor in the secretoryoriented movement of cefotiam. The transcellular transport of cefotiam in both directions was significantly depressed at a low temperature (4°C) and by 2, 4-dinitrophenol. The basolateral-to-apical transport of cefotiam was also shown to be concentration-dependent. These results suggest that a specialized transport process might participate in the transcellular transport of cefotiam. The lipophilicities of these β-lactam antibiotics were not correlated to the degree of transcellular transport, directly.
The aim of this study was to investigate the transdermal iontophoresis of a newly designed capsaicin derivative, sodium nonivamide propionate (SNP). The iontophoretic permeation of SNP from various pH buffers increased following the decrease of pH values. This trend was consistent with that of sodium nonivamide acetate (SNA) which is another synthetic analogue of capsaicin. However, the iontophoretic permeability of SNP was much lower than that of SNA. SNP was also delivered iontophoretically from hydrogel formulations. It is suggested that ionizable polymers should be avoided for iontophoretic delivery to maintain good penetration capacity of drugs. Both nonionic cellulose poplymers of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) showed higher iontophoretic flux for SNP than the others did. Furthermore, the flux of SNP leveled off with an increase in the amount of polymers in hydrogel, indicating that the viscosity of vehicles plays an important role in the permeation of SNP. Comparing the various iontophoretic application modes, the discontinuous on/off cyclic mode showed higher penetration capacity that did the continuous mode although they possessed the same electrical energy. Moreover, the desorption time of SNP from skin was approximately 20 min which was longer than that of SNA.