[Protective effect of bilirubin against sodium cholate intoxication of plant cells].
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AIM: To study the relationship between cellular membrane fluidity and relative bioavailability (Fr) of protein and peptide drugs combined with absorption enhancers after pulmonary administration in rats. METHODS: A series of model drug salmon calcitonin (sCT) solutions with 6 absorption enhancers (Brij78, sodium cholate, sodium caprylate, 2-hydroxypropyl-beta-cyclodextrin, lecithin and chitosan) were prepared and then delivered to rats by pulmonary route. Serum drug concentration was determined by radioimmunoassay method. Using the techniques of electron spin resonance and fluorescence polarography, the effects of enhancers on pulmonary cellular membrane fluidity were investigated. RESULTS: Fr values of sCT solution with some absorption enhancers (Brij78, sodium cholate, sodium caprylate, lecithin and chitosan) were significantly higher than those without enhancers. Brij78, lecithin and sodium caprylate, not only increased membrane lipid fluidity but also loosed the constitution of membrane protein. The effect of sodium cholate on membrane protein was low. Lipid fluidity was reduced and protein constitution was changed markedly, after pulmonary cellular membrane was treated by 0.5% chitosan solution. This result showed that the absorption enhancing of chitosan mainly came from its effects on membrane protein. Corresponded with lower Fr after pulmonary administration, 2-hydroxypropyl-beta-cyclodextrin (0.5% and 3%) had not significant effects on both lipid fluidity and protein constitution. CONCLUSION: The effects of enhancers on pulmonary absorption of peptide drugs in vivo might be investigated on the grounds of determination of cellular membrane fluidity in vitro.
The inhibitory effects of L-type Ca2+ channel antagonists on Na cholate-induced in vitro excystment (CIIE) of Paragonimus ohirai metacercariae were studied. At concentrations of 10 microM, nicardipine and nimodipine inhibited CIIE completely and by approximately 92%, respectively. Nitrendipine and (+/-)-verapamil inhibited CIIE by about one half and one third, respectively. Nifedipine and diltiazem did not inhibit CIIE significantly. At higher concentrations, nitrendipine at 20 microM completely inhibited CIIE, and (+/-)-verapamil at 40 microM inhibited CIIE by 93%. Nifedipine and diltiazem inhibited CIIE only slightly and little, respectively, even at 40 microM. Complete inhibition by nicardipine at 10 microM required preincubation of metacercariae with the antagonist for 15 min. The inhibitory effects of nicardipine and nimodipine were reversible, and most of the nimodipine-treated metacercariae could excyst within 1 h after being washed, but the nicardipine-treated ones started to excyst 1 h after washing. Nicardipine suppressed the active movement of encysted juveniles evoked by Na cholate, whereas nimodipine did not suppress this significantly. These results suggested that L-type Ca2+ channels appeared to be involved in CIIE of P. ohirai metacercariae and that the inhibitory effect of the channels was due primarily to factors other than the inhibition of muscular activity, probably involving the secretion and release of enzymes lytic against the metacercarial cyst wall.
The results demonstrate the biliary reabsorption of 14C-cholate, 14C-glycocholate, and 14C-taurocholate from the rat biliary tree after retrograde intrabiliary injection. It could be shown that retrograde injection of these bile salts (20 nmol) in a total volume of 40 mul leads to significantly increased biliary reabsorption in contrast to the administration in a retrograde volume of only 20 mul. These differences in reabsorption may be explained by greater reabsorption at a more proximal site in the biliary tree. Furthermore 14C-glycocholate and 14C-taurocholate are reabsorbed to a lesser extent in contrast to 14C-cholate when bile flow was restarted at once after retrograde injection in a volume of 40 mul. It is speculated that conjugation of cholate to glycine and taurine has some effect on the extent of biliary reabsorption of this bile acid. Following the results presented in this paper one might hypothize that biliary reabsorption has an important influence on bile composition i.e. the biliary excretion of bile salts.
Highly deformable hydrophilic lipid vesicles have been studied for transdermal delivery of therapeutically active small molecules and proteins. Here, we report the effects of edge activators on the formation of ultradeformable liposomes (UL) and transdermal gene delivery. Sodium cholate, sodium deoxycholate, and Tween 80 were tested as edge activators. Of the edge activators, sodium cholate and sodium deoxycholate resulted in the smaller sizes of UL and more positive zeta potentials than did Tween 80. Moreover, sodium deoxycholate-based UL showed the highest positive zeta potentials, which might lead to the firmer binding with negatively charged DNA. Following topical application onto mice, DNA complexed with UL containing either sodium cholate or sodium deoxycholate showed substantial transdermal absorption. In contrast, DNA complexed with Tween 80-based UL did not show in vivo transdermal absorption. These data suggest that UL might be of use as a transdermal delivery system of plasmid DNA, and that the choice of edge activators may play an important role in the transdermal delivery of plasmid DNA via UL.
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The use of cholic acid T tube infusion and of the Burhenne catheter has been investigated in the management of gallstones retained in the common bile duct following biliary surgery in 9 patients. Four of 7 patients treated with cholic acid infusion showed disappearance of the stones during treatment. The stones in a fifth subject were removed by a combination of cholic acid infusion (1 stone disappeared) and instrumentation with a Burhenne catheter (a second stone removed). Use of a Burhenne catheter was unsuccessful in 3 of 4 patients. Details of the technique of cholic acid infusion are given, and possible complications of the treatment are discussed. The use of cholic acid infusion for the dissolution of stones in the common bile duct is recommended.
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Dilution of phospholipid-detergent mixed micellar systems results in an increase of the fraction of monomeric detergent and, consequently, in a decrease of the effective ratio Re between non-monomeric detergent and phospholipid. The value of Re has been previously shown to be the main determinant of the state of aggregation in such mixtures: at Re values below a critical value ReSAT, the mixture is vesicular; at Re values higher than ReSOL, the mixture is micellar, whereas within the range of ReSAT-ReSOL, vesicles and micelles co-exist. Albumin binds bile salts. Therefore, in PC-cholate mixtures, Re is reduced by the presence of albumin in the system. Within the range of PC concentrations of 2-23 mM, cholate concentrations of 2-15 mM and BSA concentrations of 0-100 mg/ml, binding of cholate to BSA results in reduction of the effective cholate concentration to the extent of 0.11 mM cholate per 1 mg/ml BSA, namely up to 7 cholate molecules bind to each BSA molecule. Yet, the values of ReSAT and ReSOL are essentially independent of BSA. In addition, at any given Re value, the size of vesicles made by dilution of mixed micelles is a complex function of albumin and PC concentrations. Possible mechanistic details which may cause this effect are discussed. These effects of albumin on the state of aggregation of PC-cholate mixtures must be taken into account in studies of such mixtures in the presence of albumin when other effects of albumin (e.g., on phospholipolysis) are investigated. Practical conclusions are reached with respect to the procedures that can be used to prepare vesicles of identical composition and size in the presence of different concentrations of albumin.
DNA is the purported target of several carcinogenic and mutagenic agents. Nuclear enzymes which could generate or detoxify reactive metabolites are of major concern. Several such enzymes have been identified within nuclei, but obtaining samples with enriched content or activity is difficult, time-consuming, and uses harsh isolation techniques. Extraction of rat liver nuclear suspensions with cholate-containing buffer results in solubilization of 25-30% of the protein. Linear extraction was obtained for total protein and cytochromes P-450 and b5, NADPH-cytochrome P-450 reductase, NADH-cytochrome b5 reductase, DT-diaphorase, and microsomal-like epoxide hydrolase with specific activities comparable to values reported for isolated nuclear membrane, while the yield was five to ten times greater. Detergent extracts of rat liver nuclei were employed to study the comparative response of microsomal and nuclear enzymes to chemical treatment. While the responses to acute inductive (phenobarbital and 3-methylcholanthrene) and toxic (carbon tetrachloride and dibromochloropropane) treatments were qualitatively similar, an initiation-promotion protocol (diethylnitrosamine with phenobarbital promotion) resulted in divergent responses between the enzymes in the two subcellular fractions. Detergent extracts of nuclei offer an efficient means of recovering xenobiotic-metabolizing enzymes from rat liver nuclei, and have been utilized to demonstrate a differential response of nuclear enzymes during preneoplastic development.
The interaction of the bile salt cholate with unilamellar vesicles was studied. At low cholate content, equilibrium binding measurements with egg yolk lecithin membranes suggest that cholate binds to the outer vesicle leaflet. At increasing concentrations, further bile salt binding to the membrane is hampered. Before the onset of membrane solubilization, diphenylhexatriene fluorescence anisotropy decreases to a shallow minimum. It then increases to the initial value in the cholate concentration range of membrane solubilization. At still higher cholate concentrations, a drop in fluorescence anisotropy indicates the transformation of mixed disk micelles into spherical micelles. Perturbation of the vesicle membranes at molar ratios of bound cholate/lecithin exceeding 0.15 leads to a transient release of oligosaccharides from intravesicular space. The cholate concentrations required to induce the release depend on the size of the entrapped sugars. Cholesterol stabilizes the membrane, whereas, in spite of enhanced membrane order, sphingomyelin destabilizes the membrane against cholate. Freeze-fracture electron microscopy and phosphorus-31 nuclear magnetic resonance (31P NMR) also reflect a change in membrane structure at maximal cholate binding to the vesicles. In 31P NMR spectra, superimposed on the anisotropic line typically found in phospholipid bilayers, an isotropic peak was found. This signal is most probably due to the formation of smaller vesicles after addition of cholate. The results were discussed with respect to bile salt/membrane interactions in the liver cell. It is concluded that vesicular bile salt transport in the cytoplasm is unlikely and that cholate binding is restricted to the outer leaflet of the canalicular part of the plasma membrane.
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