Improved pharmacokinetic and lymphatic uptake of Rose Bengal after transfersome intradermal deposition using hollow microneedles

The lymphatic system is active in several processes that regulate human diseases, among which cancer progression stands out. Thus, various drug delivery systems have been investigated to promote lymphatic drug targeting for cancer therapy; mainly, nanosized particles in the 10-150 nm range quickly achieve lymphatic vessels after an interstitial administration. Herein, a strategy to boost the lymphotropic delivery of Rose Bengal (RB), a hydrosoluble chemotherapeutic, is proposed, and it is based on the loading into Transfersomes (RBTF) and their intradermal deposition in vivo by microneedles. RBTF of 96.27 ± 13.96 nm (PDI = 0.29 ± 0.02) were prepared by a green reverse-phase evaporation technique, and they showed an RB encapsulation efficiency of 98.54 ± 0.09%. In vitro, RBTF remained physically stable under physiological conditions and avoided the release of RB. In vivo, intravenous injection of RBTF prolonged RB half-life of 50 min in healthy rats compared to RB intravenous injection; the RB half-life in rat body was further increased after intradermal injection reaching 24 h, regardless of the formulation used. Regarding lymphatic targeting, RBTF administered intravenously provided an RB accumulation in the lymph nodes of 12.3 ± 0.14 ng/mL after 2 h, whereas no RB accumulation was observed after RB intravenous injection. Intradermally administered RBTF resulted in the highest RB amount detected in lymph nodes after 2 h from the injection (84.2 ± 25.10 ng/mL), which was even visible to the naked eye based on the pink colouration of the drug. In the case of intradermally administered RB, RB in lymph node was detected only at 24 h (13.3 ± 1.41 ng/mL). In conclusion, RBTF proved an efficient carrier for RB delivery, enhancing its pharmacokinetics and promoting lymph-targeted delivery. Thus, RBTF represents a promising nanomedicine product for potentially facing the medical need for novel strategies for cancer therapy.

Exploiting a Rose Bengal-bearing, oxygen-producing nanoparticle for SDT and associated immune-mediated therapeutic effects in the treatment of pancreatic cancer

Sonodynamic therapy (SDT) is an emerging stimulus-responsive approach for the targeted treatment of solid tumours. However, its ability to generate stimulus-responsive cytotoxic reactive oxygen species (ROS), is compromised by tumour hypoxia. Here we describe a robust means of preparing a pH-sensitive polymethacrylate-coated CaO₂ nanoparticle that is capable of transiently alleviating tumour hypoxia. Systemic administration of particles to animals bearing human xenograft BxPC3 pancreatic tumours increases oxygen partial pressures (PO₂) to 20-50 mmHg for over 40 min. RT-qPCR analysis of expression of selected tumour marker genes in treated animals suggests that the transient production of oxygen is sufficient to elicit effects at a molecular genetic level. Using particles labelled with the near infra-red (nIR) fluorescent dye, indocyanine green, selective uptake of particles by tumours was observed. Systemic administration of particles containing Rose Bengal (RB) at concentrations of 0.1 mg/mg of particles are capable of eliciting nanoparticle-induced, SDT-mediated antitumour effects using the BxPC3 human pancreatic tumour model in immuno-compromised mice. Additionally, a potent abscopal effect was observed in off-target tumours in a syngeneic murine bilateral tumour model for pancreatic cancer and an increase in tumour cytotoxic T cells (CD8⁺) and a decrease in immunosuppressive tumour regulatory T cells [T_reg (CD4⁺, FoxP3⁺)] was observed in both target and off-target tumours in SDT treated animals. We suggest that this approach offers significant potential in the treatment of both focal and disseminated (metastatic) pancreatic cancer.

Topical liposomal Rose Bengal for photodynamic white hair removal: randomized, controlled, double-blind study

BACKGROUND

Blond and white hair removal by laser is a complicated task with weak satisfactory results due to the deficiency in laser-absorbing chromophore.

OBJECTIVE

To investigate if repetitive sessions of photodynamic therapy (PDT) using external application of liposomal Rose bengal (RB) photosensitizer followed by intense pulsed light (IPL) exposure enables removal of gray and white hair.

MATERIALS AND METHODS

Rose bengal loaded in liposomes (LRB) was constructed, prepared in hydrogel, and was studied for some pharmaceutical properties. Penetration and selective hair follicle damage in mice skin were studied. Topical gel containing LRB was used for treating fifteen adult females who were complaining of facial white terminal hair. Unwanted facial hair was treated for three sessions at intervals of 4-6 weeks using intense pulsed light (IPL). At each session, the treatment area was pre-treated with topical LRB gel, while a control group of another 15 patients applied placebo gel before IPL treatment. Evaluations included hair regrowth, which was measured 4 weeks after each treatment session and at 6 months follow-up by counting the number of terminal hair compared with baseline pretreatment values. Treatment outcomes and complications if any were also reported.

RESULTS

Average hair regrowth in the LRB group was 56% after 3 treatment cycles. After six-months follow up, average terminal hair count compared with baseline pretreatment showed 40% reduction and no recorded side effects. A significant difference (P<0.05) was seen compared with the control group; the clinical results were promising.

CONCLUSIONS

Photodynamic hair removal using rose bengal-encapsulated liposomal gel in combination with IPL treatment showed significant efficacy in the treatment of white hair compared with a control group.

Synthesis of Amphiphilic Derivatives of Rose Bengal and Their Tumor Accumulation

It is known that the combination of laser light and its sensitizer is effective for noninvasive tumor treatment, referred to as photodynamic therapy. Using the combination of ultrasound and its sensitizer has also been suggested for a similar kind of tumor treatment, referred to as sonodynamic therapy. The purpose of this paper is to obtain such sensitizers accumulating selectively in tumors. Amphiphilic derivatives of rose bengal (RB) were synthesized to add a tumor-accumulating property to RB. One type of the synthesized RB derivatives (RBD3), having an alkyl chain with a branching carboxyl group, was found to be superior in amphiphilicity to the other types. Tumor tissue distribution of the synthesized derivatives in mice bearing colon 26 carcinoma was evaluated. It was found that RBD3s with carbon chain lengths of 12, 14, and 16 had higher concentrations in the tumor tissue than RB by more than 1 order of magnitude, several hours after administration. The concentrations correlated well with their water/1-octanol partition coefficients. Since RB is known to induce in vitro cell damage in combination with either laser light or ultrasound, the newly synthesized amphiphilic RB derivatives may be potentially useful as a tumor-selective sensitizer for both light and ultrasound.

Atelocollagen Punctal Occlusion in Dry Eye Patients

PURPOSE

To evaluate the efficacy and safety of atelocollagen punctal occlusion for dry eye patients.

DESIGN

Prospective noncomparative interventional case series.

METHODS

Atelocollagen was injected into the superior and inferior canaliculi of 52 eyes of 28 dry eye patients. Vital staining of the ocular surface, breakup time of tears (BUT), tear volume, and corneal epithelial permeability to fluorescein were examined before and 1, 2, 4, and 8 weeks after treatment.

RESULTS

Rose bengal stain, fluorescein stain, BUT, and corneal epithelial permeability to fluorescence were significantly improved 1 week after atelocollagen punctal occlusion, and the improvement was maintained for up to 8 weeks after treatment.

CONCLUSIONS

Atelocollagen punctal occlusion effectively improves ocular surface disorders in dry eye patients.

Topical rose bengal: pre-clinical evaluation of pharmacokinetics and safety

BACKGROUND AND OBJECTIVES

Rose bengal (RB) is a potent photosensitizer that has largely been overlooked as a potential photodynamic therapy (PDT) agent. In this study, the feasibility of topical delivery of RB to the epidermis has been evaluated.

STUDY DESIGN/MATERIALS AND METHODS

Topical formulations of RB were assessed on murine and rabbit skin for pharmacokinetic properties, cutaneous toxicity, and photosensitization.

RESULTS

Hydrophilic formulations (<or=1% RB) exhibited rapid, selective, uniform delivery to the epidermis, with no significant acute cutaneous toxicity in normal skin. Illumination (532 nm) elicited no acute phototoxicity for light intensities <or=100 mW/cm(2) at a light dose of 100 J/cm(2); use of higher intensities resulted in superficial thermal damage. Repeat treatment of rabbit skin (weekly for four weeks) elicited minor phototoxicity only at the highest concentration (1% RB).

CONCLUSIONS

These results indicate that RB is safe for PDT treatment of skin disorders, exhibiting negligible effects in normal skin.

Firefly luciferin-activated rose bengal: in vitro photodynamic therapy by intracellular chemiluminescence in transgenic NIH 3T3 cells

Photodynamic therapy (PDT) of cancer (1, 2) is a well-established treatment modality that uses light excitation of a photosensitive substance to produce oxygen-related cytotoxic intermediates, such as singlet oxygen or free radicals (3, 4). Although PDT is advantageous over other forms of cancer treatments because of its limited side effects, its main disadvantage is the poor accessibility of light to more deeply lying malignancies. External light sources such as lasers or lamps can be applied either noninvasively to reach tumors that lie well within the penetration depth of the light or in a minimally invasive fashion (interstitial treatments) in which optical fibers are placed intratumorally through needles. Even with the second approach, light distribution over the tumor is not homogeneous and nonidentified metastatic disease is left untreated. CL, the chemical production of light, is exemplified by firefly light emission mediated by the enzymatic (luciferase + ATP) oxidation of D-luciferin to oxyluciferin (5). This mobile light source is a targetable alternative to external sources of illumination. Here we show the in vitro photodynamic effect of rose bengal activated by intracellular generation of light, in luciferase-transfected NIH 3T3 murine fibroblasts.

Site-directed photochemical disruption of the actin cytoskeleton by actin-binding Rose Bengal-conjugates

The in situ light-induced, non-enzymatic digestion of cytoskeletal actin by a xanthene dye conjugated to heavy meromyosin, anti-actin antibodies and/or anti-myosin antibodies is reported. The dye Rose Bengal was conjugated to either anti-actin antibodies, anti-myosin antibodies or heavy meromyosin. Under our experimental conditions, visible light induced the non-enzymatic breakdown of cytoskeletal actin when mammalian tissue culture cells were probed either with Rose Bengal-conjugated anti-actin and/or anti-myosin antibodies. Similar results were obtained when tissue culture cells were probed with Rose Bengal-conjugated heavy meromyosin before irradiation with visible light. The in situ photochemical reaction depended on the presence of actin-binding Rose Bengal-conjugates.

Localization of rose bengal, aluminum phthalocyanine tetrasulfonate, and chlorin e6 in the rabbit eye

PURPOSE

The localization and site of action of photosensitizers in the eye may be important for photodynamic therapy for fundus disorders but remain poorly understood for most agents. We investigated the intraocular localization of xanthene, phthalocyanine, and chlorin photosensitizers by using fluorescence microscopy and digital fundus fluorescence angiography.

METHODS

Rose bengal (40 mg/kg), aluminum phthalocyanine tetrasulfonate (CASPc) (5 mg/kg), or chlorin e6 (2 mg/kg) was intravenously administered to albino rabbits. The eyes were enucleated and examined by means of fluorescence microscopy 5, 20, 60, and 120 minutes and 24 hours after dye injection. In vivo digital fundus fluorescence angiography with use of rose bengal (2-4 mg/kg), CASPc (2 mg/kg), and chlorin e6 (2 mg/kg) was performed.

RESULTS

For all agents studied pathologically, there was moderate fluorescence from the choroid and retinal pigment epithelium 5 minutes after dye injection. Mild fluorescence detected from the photoreceptor outer segments at 5 minutes was increased at 20 minutes. Angiographic studies with use of rose bengal, CASPc, and chlorin e6 revealed differences in the pattern and rate of photosensitizer accumulation.

CONCLUSIONS

Rose bengal, CASPc, and chlorin e6 accumulate rapidly in the choroid and retinal pigment epithelium and less rapidly in the outer retina. Differences in ocular localization of these photosensitizers were demonstrated. The significance of these findings for potential photodynamic therapy with these agents requires further investigation.

Photosensitizer accumulation in spontaneous multidrug resistant cells: a comparative study with Rhodamine 123, Rose Bengal acetate and Photofrine

The influence both of overexpression of multidrug transporter proteins and of phenotype changes occurring in cells developing spontaneous resistance on the accumulation of photosensitizer molecules was studied on two tumor-derived cell lines (B16, A2780) expressing the MDR-1 phenotype. Rhodamine 123, Rose Bengal acetate (a fluorogenic substrate that is restored to the native active molecule by specific enzyme activity inside cells) and Photofrin were considered. The two resistant variants accumulate Rhodamine 123 to a lesser extent than the respective wild types. Treatment with verapamil markedly enhances Rhodamine 123 accumulation in resistant cells, blocking the drug's extrusion. The amount of Rose Bengal is larger in resistant cells than in wild type cells. Verapamil does not affect drug accumulation, although it significantly impairs the efflux process. The results are explained by the enhancement of both membrane traffic and esterase activity resulting in intracellular Rose Bengal production that counterbalances the increased ability in the outward transport of resistant cells. Photofrin is accumulated to a lower degree in resistant than in wild type cells. Verapamil does not alter the drug accumulation, although the release process is somewhat affected. Different intracellular turnovers of Photofrin take place in the cell variants, and the release of the monomeric fluorescent fractions is greater in resistant than in wild type cells.

Drug delivery in poly(lactide-co-glycolide) nanoparticles surface modified with poloxamer 407 and poloxamine 908: in vitro characterisation and in vivo evaluation

Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles of 150-nm mean size were produced by an interfacial deposition method. The polar model drug Rose Bengal was successfully loaded into the nanoparticles during production and the surface of these particles was subsequently modified with poloxamer 407 and poloxamine 908 in order to create a steric stabilising layer of PEG on the surface. Drug loading was low (<1%) which can be attributed to the polar nature of the drug and the small size of the nanoparticles. Drug release was biphasic with 50% release measured within 30 min in serum. After intravenous injection in rats, the drug loaded nanoparticles substantially avoided capture by the Kupffer cells of the liver as compared to free drug. The half-life of Rose Bengal in the blood stream when administered in the nanoparticles was greatly extended with approximately 30% remaining after 1 h as compared to only 8% of Rose Bengal left 5 min after administration in solution. These surface modified nanoparticles would have potential as carriers for drugs to specific sites within the body or for slow release of drug within the circulation.

Photosensitized production of singlet oxygen

Photosensitization is a simple and controllable method for the generation of singlet oxygen in solution and in cells. Methods are described for determining the yield of singlet oxygen in solution, for measurement of the rate of reaction between singlet oxygen and a substrate, and for comparing the effectiveness of singlet oxygen generated by different photosensitizers in cells. These quantitative measurements can lead to better understanding of the interaction of singlet oxygen with biomolecules.

Effects of lacrimal drainage occlusion with nondissolvable intracanalicular plugs on hydrogel contact lens wear

PURPOSE

To investigate effects of lacrimal drainage occlusion with intracanalicular silicone plugs in hydrogel lens wearers with the symptom of dryness. Effects of rewetting drops in combination with the plugs were also evaluated.

METHODS

A 6-week, prospective, double masked, placebo-controlled study design was followed. Thirty-five patients (26 females and 9 males) were entered into the study based on specific symptoms and signs of dry eye with hydrogel lens wear. Baseline symptoms, noninvasive prelens tear film break-up time, lens water content, fluorescein, and rose bengal staining were recorded. Herrick Lacrimal Plugs were inserted into both canaliculi of one previously randomized eye by an independent investigator. The fellow eye was manipulated in a sham procedure. Symptoms and signs were followed over 4 weeks. Nonpreserved rewetting drops were used in both eyes during the 5th week. Symptoms and signs were again followed.

RESULTS

Symptoms improved more significantly in the plugged eye than the control eye after insertion of the plugs, and again after use of the drops. This improvement diminished in some of the patients. Prelens tear film break-up time was not significantly changed. Water content of all lenses combined increased only in the plugged eye with the use of drops. Fluorescein staining decreased significantly in the plugged eye. Rose bengal staining showed a slight decrease in the plugged eye.

CONCLUSIONS

Intracanalicular silicone plugs offer improvement of symptoms and signs of dryness in this population. There seems to be some decrease in improvement of symptoms with the plugs over time. Concurrent use of rewetting drops increases the benefits.

Hepatobiliary excretion of bile acids and rose bengal in streptozotocin-induced and genetic diabetic rats

Divergent opinions regarding the effect of streptozotocin- (STZ) induced diabetes on bile flow rate may be due to the differing lengths of time after STZ administration at which bile flow was measured. Also, the biliary excretion of bile acids can influence the canalicular transport of several organic anions. Therefore, the hepatic clearance of the bile acid-dependent organic anion rose bengal was studied over a 30-day period in STZ-induced insulin-dependent Sprague-Dawley diabetic rats with elevated bile acid pools and in fatty noninsulin-dependent diabetic and lean Wistar rats. Excretion of total bile acids and rose bengal was higher in diabetic rats than in Sprague-Dawley control or lean or fatty Wistar rats. Depletion of bile acids for 10 hr in the 30-day STZ rat prevented the increased excretion of rose bengal. Bile flow rates in fatty and lean Wistar rats were similar to that in Sprague-Dawley controls. Increased bile acid excretion 7 and 14 days after STZ was not accompanied by the expected significant increase in bile flow, reflecting decreased bile acid-independent bile flow, regardless of method of calculation of bile flow (per g liver or per kg body weight). By 30 days, there were significant increases in bile acid excretion and bile flow. The increased clearance of rose bengal 7 days after STZ indicates that pathophysiological changes in the hepatocyte begin soon after the initiation of diabetes. Studies of taurocholate uptake into liver plasma membrane vesicles indicated that the maximal velocity of transport across the basolateral membrane was increased with no change in Km. This change was not observed in vesicles from insulin-treated diabetic rats. Therefore, studies employing STZ need to allow time for STZ toxicity to be overcome and for the pathology of diabetes to become established, to accurately reflect the diabetic condition.

Hydroxypropyl methylcellulose for the treatment of severe dry eye associated with Sjögren's syndrome

Our purpose was to evaluate the efficacy of a new formulation of methylcellulose, preservative-free 0.5% hydroxypropyl methylcellulose (HPMC), for the treatment of dry eye. In the clinical part of our study, two groups of dry-eye patients, those with Sjögren's syndrome (SS) and those without (non-SS), were treated topically with 0.5% HPMC and evaluated for symptoms, ocular surface vital staining, tear breakup time (BUT), and tear evaporation rate from the ocular surface at 40% ambient humidity (TEROS40). In the in vivo part of the study, rose bengal uptake was measured in human conjunctival epithelial cells, which were cultured and incubated with or without 0.5% HPMC. Although symptoms improved in both groups, rose bengal and fluorescein staining and BUT improved significantly only in the SS group. TEROS40 increased for 30 min after instillation of 0.5% HPMC, but not after use of 0.1% sodium hyaluronate or saline-based artificial tears. Rose bengal uptake by cultured conjunctival epithelial cells was blocked by 0.5% HPMC. These findings suggest that 0.5% HPMC provides long coverage of and protection for the ocular surface. Patients with severe dry eye, such as in SS, are good candidates for this treatment.

Hepatic transport of rose bengal by perfused rabbit liver: the effect of albumin binding on the unidirectional rate constants

The effect of albumin on the unidirectional rate constants for the hepatic transport of rose bengal was studied using perfused rabbit livers. Rabbit livers were perfused in a recirculating system with albumin concentrations between 10 and 600 microM and the disappearance of I-125 rose bengal following a bolus injection was recorded. A distributed model of hepatic transport was used to estimate the rate constants for influx into cells, efflux from cells to plasma and biliary excretion. When the rate constants were corrected for albumin binding, the influx, but not the efflux or excretion constant, was a steeply rising function of the perfusate albumin concentration. The result that the influx but not efflux constant is albumin dependent suggests that the phenomenon is not due to slow diffusion across an unstirred fluid layer or to nonequilibrium binding within such a layer. The possibility that the albumin-dependent influx is due to a direct exchange of rose bengal between albumin and a membrane carrier protein is also considered. The independence of the efflux constant and the albumin concentration makes this hypothesis less tenable. However, these data are consistent with the facilitation of albumin-ligand dissociation by liver cells. This analysis represents the first reduction to practice of distributed modeling of disappearance curves. The fact that the excretion constant is independent of the perfusate albumin concentration serves to validate the model that has previously only been considered on theoretical grounds.

Chronic voluntary exercise may alter hepatobiliary clearance of endogenous and exogenous chemicals in rats

A chronic voluntary exercise paradigm, which mimics the exercise pattern of many humans, influences the hepatic clearance of several organic anions and a bile acid, whereas a neutral organic compound is seemingly unaffected. To extend these observations, the present work has evaluated in female Sprague-Dawley rats the effect of 6 weeks of voluntary running on the hepatobiliary elimination of endogenous bile acids and glutathione and exogenously injected rose bengal, digoxin, and acetaminophen. Inactive rats had mobility limited to their cages, whereas exercised rats had free access to a 44-in running wheel. In comparison to weight-matched sedentary rats, the exercised rats ran 4.3 +/- 0.3 miles/day, consumed 45% more food daily, had slightly greater liver/body weight ratios, and slightly elevated basal bile flow rates. Biliary excretion of endogenous bile acids was increased significantly, and excretion of reduced and oxidized glutathione was increased in exercised rats by 190% and 173% of sedentary levels, respectively. Total clearance, biliary clearance, and maximal biliary excretion of the injected organic anion rose bengal (60 mumol/kg) were elevated in exercised rats by 86%, 440%, and 85%, respectively. In contrast, there were no observed differences in pharmacokinetic parameters, serum elimination, or biliary excretion for the clinically important cardiac glycoside digoxin (dose of 100 nmol/kg). Finally, study of the analgesic acetaminophen (330 mumol/kg) revealed that total and biliary clearances were increased by 37% and 42%, respectively, in exercised rats, whereas steady-state volume of distribution and elimination half-life were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Biliary excretion of cholephilic organic dyes in glutathione-depleted rats

Sprague-Dawley rats were treated with a combination of buthionine sulfoximine (2.5 mmol/kg body wt) and diethyl maleate (6.2 mmol/kg). After 4 h, the hepatic glutathione was depleted to 0.02 +/- 0.01 mumol/g liver (mean +/- SD, n = 6) (4.73 +/- 0.29 mumol/g in controls (n = 6), p < 0.005). The bile flow rate was lower in treated animals than in controls (39.0 +/- 11.2 vs. 73.7 +/- 13.7 microliters.kg-1.min-1, p < 0.005). Bile concentrations of bile acids, phospholipids, and cholesterol were not changed compared to controls, while glutathione was virtually absent from the bile. A bolus of indocyanine green (6.5 mumol/kg), rose bengal (6.5 mumol/kg), or sulfobromophthalein-glutathione conjugate (20 mumol/kg) was injected i.v. and the biliary excretion was monitored. In glutathione-depleted rats, the excretion of indocyanine green was delayed, and the cumulative excretion in 90 min was 36 +/- 8% (n = 6) of the injected dose (79 +/- 18% in controls (n = 7), p < 0.005). The bile concentration of indocyanine green was lower in the glutathione-depleted rats than in controls, while the other dyes increased. The plasma disappearance curve of indocyanine green was not significantly altered by the treatment, whereas the hepatic retention of indocyanine green 90 min after the injection was significantly increased (58 +/- 12% of the injected dose vs. 8 +/- 2% in controls, p < 0.005). The results indicate that depletion of hepatic glutathione inhibits biliary excretion of indocyanine green.

Effect of sodium orthovanadate on the hepatobiliary clearance of rose bengal in streptozotocin-induced diabetic rats

Sodium orthovanadate is known to promote glucose uptake in muscle and adipose tissues and has been suggested as a possible oral hypoglycemic agent. In addition, insulin-dependent diabetes has been shown to alter the hepatobiliary clearance of several drugs in rats. This study has determined whether orthovanadate, like insulin, can reverse diabetes-induced changes in the biliary excretion of endogenous bile acids and in the hepatobiliary clearance of rose bengal. Six groups of male Sprague-Dawley rats were used; normal, insulin-treated normal, vanadate-treated normal, diabetic, insulin-treated diabetic, and vanadate-treated diabetic. Diabetes was induced by injection of streptozotocin (45 mg/kg, i.v.). One week later, insulin (2-4 U/day, s.c.) and sodium orthovanadate (877 +/- 82 mumol/kg/day, p.o.) treatments were initiated. After 4 weeks, the clearance and biliary excretion of rose bengal (60 mumol/kg, i.v.) were determined for 3 hr. Bile flow rate, rose bengal excretion, and excretion of endogenous bile acids were unchanged in the two treated normal groups and in the insulin-treated diabetic rats. These parameters were increased in untreated diabetic and vanadate-treated diabetic rats as compared with normal. Pharmacokinetic analyses indicated that total and biliary clearances of rose bengal were increased in diabetic rats and that orthovanadate did not reverse these changes. However, liver weight and serum glucose concentrations were reduced by orthovanadate treatment. These data indicate that the oral insulinomimetic chemical sodium orthovanadate effectively reversed some, but not all, of the diabetes-induced alterations of hepatic function.

Nonlinear pharmacokinetics of hepatobiliary transport of rose bengal in rats after i.v. bolus administration with varying doses

To investigate the nonlinear kinetics in the hepatobiliary transport of rose bengal (RB), the time profiles of plasma concentration and biliary excretion rate after its i.v. administration at various doses were measured in rats. The total body clearance decreased remarkably with increased dose. The hepatic uptake clearance also showed a similar dose dependency, and saturation of hepatic uptake at least partly accounts for the dose-dependent change in total body clearance. The peak biliary excretion rate approached the transport maximum (approximately 150 nmol min-1 kg-1) with increased dose. To further clarify which process in RB hepatobiliary transport has nonlinearity, we analysed thus obtained data based on a three-compartment model. The hepatic uptake and sequestration rate constants decreased remarkably with increased dose. The initial hepatic uptake rates assessed from the plasma disappearance rate during the early phase fit well to the Michaelis-Menten equation with a saturable and a nonsaturable component. The maximum uptake velocity and Michaelis constant were 4.7 mumol min-1 kg-1 and 360 microM, respectively. That hepatic uptake has a much higher capacity (about 30 fold) than biliary excretion suggests that biliary excretion can be a rate-determining process in the overall hepatobiliary transport of RB. We conclude that the saturation of both hepatic uptake and biliary excretion could be the main causes for the nonlinear pharmacokinetics of hepatobiliary transport of RB.

A novel transcellular transport pathway for non-bile salt cholephilic organic anions

Non-bile salt cholephilic organic anions comprise a single class of nonhomologous ligands having a range of hydrophobicity. Hydrophobicity enhances the hepatic extraction of cholephiles as well as their partitioning into secreted biliary lipid particles. When hydrophobicity is correlated with patterns of biliary excretion for studying transcellular transport, however, the more hydrophobic probes are unsuitable. Specifically, with the isolated perfused rat liver technique, the excretory times for sulfobromophthalein and rose bengal were significantly longer compared with that for the much more hydrophilic analogue phenol red (PR), which showed only a single, nearly symmetrical excretory peak at 10 min. Colchicine affected the apparently well-defined PR pathway only at a saturation dose (10,000 times the tracer dose). In contrast, the effect of a different perturbant, monensin, was striking at a tracer dose of PR, but was less evident at a saturation dose. The combined administration of colchicine and monensin had no additive inhibitory effect on PR excretion at tracer doses. At a saturation dose of PR, where monensin is less inhibiting, however, a significant additive inhibitory effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

[Permeability of the hemato-ophthalmic barrier in uveitis]

The results of examining the hematoophthalmic barrier permeability by radiometry and biotests with anterior chamber and vitreous humor are analyzed. Injection of the radiopharmaceutical into the vorticose veins provides the most effective pharmacokinetics, vs. suprachoroidal and subconjunctival injections. In toxis allergic uveitis the penetration of radiopharmaceuticals into the internal media of the eye (anterior chamber humor and vitreous body) is intensified, and dexason therapy of an inflammatory process in the vascular coating reduces this penetration.

[Hepatic scintigraphy using 123I-rose bengal]

The paper is devoted to the experience in diagnostic investigations using rose bengal, labeled with half-life 123I (123I-RB). The drug was synthesized in the B. P. Konstantinov Leningrad Institute of Nuclear Physics, USSR Academy of Sciences. Analysis of the results of investigations of 201 patients with diseases of the liver and biliary tracts revealed the advantages of 123I-RB over standard RPs of similar diagnostic purpose. Owing to low radiation exposure one could use higher activity (up to 120 MBq and more) of the drug. It made it possible to combine a study of the functional parameters of the hepatobiliary system and obtaining scintigraphic data on the structure of the liver and biliary tracts. 123I-RB is the best radiodiagnostic agent for a study of function and topography of the liver in patients with an increased blood level of bilirubin.

Protein-mediated hepatic uptake of rose bengal in analbuminemic mutant rats (NAR). Albumin is not indispensable to the protein-mediated transport of rose bengal

Recent kinetic studies using in situ perfused rat liver suggested that the hepatic uptake of extensively albumin-bound ligands is mediated primarily by direct interaction of the albumin-ligand complex with the hepatocyte surface rather than by the small unbound fraction of ligand, as has been generally believed [Ockner et al., Am. J. Physiol. 245, G13 (1983)]. In order to investigate this mechanism in vivo, rose bengal (RB) was injected iv to the normal and Nagase analbuminemic mutant rats (NAR) and both the pharmacokinetic parameters and the serum protein binding parameters for the two groups were compared. The serum disappearance curves of RB in normal rats and NAR were almost superimposed, and no significant difference in various pharmacokinetic parameters including the hepatic uptake clearance (k12V1) was observed between the two groups. Nevertheless, the unbound fractions of RB in serum were approximately 4-fold (equilibrium dialysis method) and 10-fold (spectrophotometric method) higher than those in normal rats. However, in both groups of rats RB is extensively bound to plasma proteins and more than 99.8% of RB in the plasma exists as the protein-bound form. The intrinsic ability of the two groups of rats to take up unbound RB was compared using isolated liver cells. No significant difference between the two groups was observed in the initial velocity of uptake. From these findings, we concluded that the hepatic uptake of RB is primarily driven by the serum protein-bound form and not by the unbound form and that the serum protein-mediated uptake mechanism of RB was not specific only for serum albumin but also for other serum proteins.(ABSTRACT TRUNCATED AT 250 WORDS)