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PubMed1998

Calcium absorption from small soft-boned fish.

The prevalence of osteoporosis in developing countries is low compared to most industrialised countries despite an apparent low Ca intake. It is possible, however, that food surveys have overlooked important Ca sources in developing countries. Small fish eaten with the bones can be a rich source of Ca, even though Ca from bone may be considered unavailable for absorption. In the present study, absorption of Ca from indigenous Bengali small fish was compared with the Ca absorption from milk. Ca absorption from single meals was determined in 19 healthy men and women (21-28 y). Each subject received two meal types on two separate occasions. Both meals consisted of white wheat bread, butter and ultra pure water with the main Ca source being either small Bengali fish (397 mg Ca in total) or skimmed milk (377 mg Ca in total). The meals were extrinsically labelled with 47Ca, and whole-body retention was measured on day 8, 12, 15 and 19 after intake of each meal. The labelling procedure was evaluated by an in vitro method. The calculated absorption of Ca as measured with 47Ca whole-body retention was 23.8 +/- 5.6% from the fish meal and 21.8 +/- 6.1% from the milk meal (mean +/- SD), which was not significantly different (p = 0.52). Even after correction for an incomplete isotope exchange, as indicated by the in vitro study, Ca absorption was similar from the two meal types. It was concluded that Ca absorption from small Bengali fish was comparable that from skimmed milk, and that these fish may represent a good source of Ca.

Absorption↗
PubMed1998

An in vivo study of the gastrointestinal absorption site for zinc chloride in mice.

The experimental model presented below enables quantitation of the uptake of zinc (Zn++) into gastrointestinal mucosal cells in vivo using gamma-counting of 65Zn. Experiments were performed in mice fed their normal diet under natural physiological conditions. The in vivo site(s) of significant zinc absorption may thereby be identified. Absorption of zinc was extensive during the first hour after administration of a single oral dose of ZnCl2. Apparently, absorption continued during at least eight hours postdosage, and probably continued for 48 hours. The intestinal mucosal labelling profile for zinc did not depend on dose size or the mode of administration (single oral doses or in drinking water). The duodenum and ileum were important sites for rapid zinc absorption. A continuous, slower absorption of zinc may take place in the jejunum. The stomach, caecum and colon appeared to be insignificant sites of zinc absorption. The transit time for zinc was very short as large quantities of zinc passed through the small intestine within one hour. In contrast to other studies, the intestinal labelling profile or the extent of zinc absorption were not changed in mice that received Tetraethylthiuram disulfide (TTD) in their food.

Alcohol Deterrents↗
PubMed1998

Transurethral resection syndrome: effect of the introduction into clinical practice of a new method for monitoring fluid absorption.

STUDY OBJECTIVE: To determine the effects of introduction of a new monitoring system for fluid absorption during transurethral resection of the prostate (TURP) using an irrigating solution containing 0.5% alcohol. STUDY DESIGN: Prospective clinical investigation, with implementation of statistical process control. SETTING: Inpatients for TURP at a major non-university teaching hospital. PATIENTS: 312 male ASA physical status I, II, III, and IV patients scheduled for TURP. INTERVENTIONS: Intraoperative breath alcohol levels were measured for detection of fluid absorption. MEASUREMENTS AND MAIN RESULTS: Calculation of the amount of fluid absorbed using measured breath alcohol values. Process variability (i.e., numbers of patients with significant fluid absorption) was defined by statistical process control tools. No trend change of prevalence of fluid absorption was noted until 150 procedures had been completed. Reduction of prevalence of significant fluid absorption was noted and no patients were treated postoperatively in the intensive care unit. No relevant side effects were seen in patients with significant fluid absorption. No mortality and no severe clinical morbidity was seen after the introduction of the new monitoring. CONCLUSION: Using an irrigating fluid marked with 0.5% ethanol resulted in a decreased prevalence of fluid absorption over time.

Absorption↗
PubMed1999

Detection of fluid volume absorption by end-tidal alcohol monitoring in patients undergoing endoscopic renal pelvic surgery.

STUDY OBJECTIVE: To determine the risk of relevant fluid absorption (calculated volume above 500 ml) during endoscopic procedures of the renal pelvis. DESIGN: Prospective clinical investigation with implementation of statistical process control tools (SPC). SETTING: Nonuniversity teaching hospital. PATIENTS: 62 consecutive ASA physical status I and II patients scheduled for endoscopic renal pelvic surgery with general anesthesia. INTERVENTIONS: Intraoperative measurement of breath alcohol for detection of fluid absorption. Irrigation fluid (0.9% saline) with 1% alcohol for tracing the irrigation fluid. MEASUREMENTS AND MAIN RESULTS: Calculation of the amount of fluid absorbed using breath alcohol values. Process variability (numbers of patients with relevant fluid absorption) defined by SPC. The prevalence of fluid absorption in endoscopic renal pelvic surgery was 6%. Peak fluid absorption during a vascular route was detected by the monitoring. Monitoring was easily introduced into routine clinical practice. No relevant side effects due to the monitoring were seen in patients with relevant fluid absorption. There was no mortality, but two patients with detected severe fluid overload were admitted to the intensive care unit for treatment. CONCLUSION: Breath alcohol levels during general anesthesia for endoscopic renal pelvic surgery were technically simple to measure. Our results show the predictive value of alcohol monitoring, which has been previously demonstrated only for transurethral prostatectomy. The prevalence of relevant fluid absorption was 6% compared to 13% during transurethral resection of the prostate.

Absorption↗
PubMed1998

Intestinal absorption of fluorescence-derivatized cationic peptide 001-C8-NBD via adsorptive-mediated transcytosis.

The intestinal absorption of an intact oligopeptide was investigated in rats using a synthetic cationic peptide, 001-C8 (H-MeTyr-Arg-MeArg-D-Leu-NH(CH2)8NH2). The peptide was coupled with 4-nitrobenzo-2-oxa-1,3-diazole (NBD) to prepare a fluorescence-labeled derivative 001-C8-NBD (H-MeTyr-Arg-MeArg-D-Leu-NH(CH2)8NH-NBD) for the purpose of quantification. The degradation half-life of 001-C8-NBD in jejunal homogenate (1 mg/mL) was 99.5 min, which was significantly longer than that of natural leucine enkephalin (1.14 min). The absorption of 001-C8-NBD was evaluated by the vascular-perfusion method. Intact 001-C8-NBD appeared in the blood time-dependently and the absorption volume at 30 min (2.75 +/- 0.14 microL/cm intestine) was significantly larger than that of [3H]PEG 900 (0.88 +/- 0.13 microL/cm intestine), of which membrane permeability is very low. The absorption of 001-C8-NBD was greatly reduced by an adsorptive-mediated endocytosis inhibitor, protamine (10 mM). No inhibition of the absorption of [3H]PEG 900 by protamine was observed. The intestinal absorption was also measured by an in vivo loop method. The absorption clearance of 001-C8-NBD measured by this method (0.083 +/- 0.008 microL/min/cm intestine) was comparable to that obtained by the vascular perfusion method (0.092 +/- 0.005 microL/min/cm intestine). All of these data suggested that 001-C8-NBD was absorbed as the intact oligopeptide in the intestine in vivo. Adsorptive-mediated transcytosis is suggested to have enormous potential as an oral delivery system for peptide and/or protein drugs.

Animals↗
PubMed2000

The effect of high intakes of casein and casein phosphopeptide on calcium absorption in the rat.

The effect of the level or source of dietary protein or protein-derived peptides on Ca absorption is not well understood. We determined, therefore, the influence of habitual dietary casein level, meal casein and meal casein phosphopeptide (CPP) on Ca absorption in the rat. True fractional Ca absorption was investigated in male 7-week-old rats, Wistar strain, in three separate studies using a faecal 47Sc: 47Ca ratio method. In studies A and C, rats (n 8 per group) were fed on a purified diet containing 200 g casein/kg for 2 weeks. Rats were then given a 47Ca-labelled meal (10 g) containing (per kg) either 0, 100, 200, or 300 g casein (study A) or 0, 100, 200, 350 or 500 g CPP (study C). In study B, rats (n 24 per group) were fed on a purified diet containing (per kg) either 200, 350 or 500 g casein for 2 weeks. Each group was then further randomized into three groups (n 8 per group) and given a 47Ca-labelled meal (10 g of the same diet) containing (per kg) either 200, 350 or 500 g casein. Ca absorption from a meal was unaffected by increasing meal casein concentration from 0 to 300 g/kg (study A), but was increased with a meal casein content of 500 g/kg (study B). Fractional Ca absorption decreased with increasing usual dietary casein intake in the range 200-500 g/kg (study B), suggesting intestinal adaptation. Ca absorption was unaffected by inclusion of 100 g CPP/kg in a single meal but was significantly (P < 0.001) reduced by 200, 350 and 500 g CPP/kg meal, with no evident dose-relationship. Thus, while Ca absorption was enhanced by high-casein meals, the mechanism remains unclear.

Animals↗
PubMed1998

Comparison of absorption of nutrients and secretion of water between oligomeric and polymeric enteral diets in pigs.

In patients who require enteric tube-feeding the osmolality of the formulas is assumed to play an important role. There is the dilemma that osmolality increases as the digestibility of formulas is enhanced by means of degradation of the nutrients. Hitherto there have been no reports of whether there are differences in nutrient absorption and water fluxes between iso-osmotic polymeric and hyperosmotic oligomeric diets. We therefore investigated absorption of nutrients and net fluxes of water during perfusion of a 1.5 m jejunal segment with oligomeric, polymeric and commercial oligopeptide diets either in the absence of pancreatic juice or with concomitant infusion of pancreatic enzymes. In the absence of pancreatic juice the absorption rates of the polymeric diet and the commercial oligopeptide diets reached 58.0 and 84.5% respectively of that of a completely-hydrolysed hyperosmotic oligomeric diet. The concomitant infusion of pancreatic enzymes with the polymeric and oligopeptide diets significantly increased the absorption rates of nutrients and energy. The highest absorption rate of energy occurred with the commercial formula Survimed (Fresenius, Bad Homburg, Germany), probably due to an optimal composition of the macronutrients. The increase in absorption due to the degradation of nutrients by pancreatic enzymes was associated with an increase in net water secretion and flow-rate, reaching similar values to those with the hyperosmotic oligomeric diet. It may be concluded that iso-osmotic oligopeptide formulas require further pancreatic hydrolysis for optimum absorption. In patients with normal pancreatic secretion, oligopeptide formulas have no advantage over polymeric diets. In patients with reduced pancreatic secretion, either completely-hydrolysed hyperosmotic oligomeric diets or polymeric diets supplemented with pancreatic enzymes are appropriate.

Animals↗
PubMed2004

Adsorptive and absorptive contributions to the gas-particle partitioning of polycyclic aromatic hydrocarbons: state of knowledge and recommended parametrization for modeling.

Four contrasting descriptions of the gas-particle partitioning of SOCs are currently used: the Junge-Pankow adsorption model, the empirical Finizio organic matter (OM) absorption relationship, the Harner-Bidleman OM absorption model, and a dual black carbon (BC) adsorption and OM absorption model. Use of these four descriptions in a box model resulted in very different global fates, particularly for PAHs such as chrysene and benzo[a]pyrene. By reviewing published gas-particle distributions of PAHs, we found evidence for both absorptive and adsorptive contributions. Based on results from laboratory and controlled field studies we suggest that on average, octanol-air partitioning (Koa) is a good approximation for the OM absorption of PAHs. However, higher concentrations in particles than could be explained by OM absorption were found in selected gas-particle partitioning field studies, which were corrected for gaseous adsorption to the filter. We argue that adsorption onto BC is responsible for most of the additional sorption. Apparent adsorption coefficients to BC, K(BC-air), were derived from field studies and showed good agreement with those predicted by adsorption onto diesel soot. For atmospheric long-range transport models we suggestthe use of a dual OM absorption and BC adsorption model, with BC properties being approximated by diesel soot: Kp = 10(-12) (f(om) 1/rho(oct) Koa + fBC/rho(BC) K(soot-air) a(atm-BC)/a(soot)). We hypothesize that kinetic constraints related to shell-like particle structures might lead to deviations from sorption equilibrium and higher particle-borne fractions of PAHs in particular at remote sites.

Absorption↗
PubMed2005

Tissue iron distribution and adaptation of iron absorption in rats exposed to a high dietary level of NaFeEDTA.

Although it has been shown that iron absorption from NaFeEDTA, a promising iron fortificant, is effectively down-regulated in iron-loaded rats, effects of prolonged exposure to high dietary levels of NaFeEDTA are not well understood. The objectives of this study were to determine whether rats can adapt to a high dietary level of NaFeEDTA by down-regulating iron absorption, and to determine effects on tissue iron distribution, with or without an iron absorption inhibitor. Male Sprague-Dawley rats were exposed to diets supplemented with FeSO4 or NaFeEDTA at 1200 mg of Fe/kg of diet, with or without tea, for 27 days. Iron absorption measured by whole-body counting before and after exposure showed that rats adapted to the high dietary level of FeSO4 or NaFeEDTA by down-regulating iron absorption to a similar extent. However, nonheme iron concentrations in liver and spleen were about 35-50% lower, whereas the concentration in kidney was about 300% higher in rats fed NaFeEDTA, compared to rats fed FeSO4. Tea had no major impact on iron absorption or iron status, regardless of iron source. Our results showed that although iron absorption was down-regulated similarly, body iron distribution was markedly different between rats exposed to FeSO4 and those exposed to NaFeEDTA. Further studies are warranted to determine the effects of prolonged exposure to dietary NaFeEDTA on kidney iron accumulation and kidney function.

Absorption↗
PubMed1996

Interaction of taurine on baclofen intestinal absorption: a nonlinear mathematical treatment using differential equations to describe kinetic inhibition models.

Previous studies showed that the in situ absorption of baclofen in rat jejunum was inhibited by beta-alanine, a nonessential amino acid, and therefore mediated, at least in part, by some beta-amino acid carrier. In this paper a similar study was undertaken using taurine, a sulfonic beta-amino acid, in order to evaluate its effect and to establish a general inhibition model. To achieve this goal, remaining concentrations of inhibitor were also measured and incorporated into the model. Previously, kinetic absorption in situ parameters for taurine in free solution were obtained: Vm = 27.73 +/- 9.99 mM h-1, K(m) = 8.06 +/- 2.82 mM, Ka (passive difussion component) = 0.40 +/- 0.28 h-1. Isotonic solutions containing 0.5 mM baclofen with starting taurine concentrations ranging from 0 to 100 mM were perfused in rat jejunum, and the remaining concentrations of both compounds were measured. The apparent rate pseudoconstant of the drug clearly decreased as the remaining taurine concentration increased. The interaction can be described as a complete competitive inhibition plus a second component, K, noninhibited, K = 0.58 (+/- 0.03) h-1, Ki = 20.62 (+/- 4.04) mM, Vmi = 28.12 (+/- 6.12) mM h-1, Kmi = 11.71 (+/- 2.53) mM, Kai = 0.47 (+/- 0.10) h-1. A residual absorption of baclofen in the presence of high taurine concentrations was observed, which should be attributed to another transport system not associated with the taurine carrier. In order to elucidate whether or not taurine and beta-alanine carriers are two separate entities that baclofen can use for absorption, further experiments using beta-alanine and taurine together as inhibitors (baclofen, 0.5 mM; beta-alanine, 50 mM, and taurine, 50 mM) were developed. Results indicated that baclofen and both amino acids share the same carrier in the intestinal absorption process. We have completed studies using leucine, taurine, and GABA together as inhibitors of drug absorption. An isotonic perfusion solution of 0.5 mM baclofen in the presence of 50 mM leucine, 25 mM taurine, and 25 mM GABA was perfused. Under these conditions the absorption rate pseudoconstant of baclofen decreases until 0.080 h-1 (+/- 0.069). Practical implications of these phenomena are briefly discussed.

Animals↗
PubMed1999

Validation of a biophysical drug absorption model by the PATQSAR system.

Absorption rate constants (in situ rat gut technique) and in vitro antibacterial activities of twenty fluoroquinolones have been evaluated. A biophysical model that relates the absorption of the compounds with their lipophilicity was fitted. The model considers the absorption process from the intestinal lumen as the sum of two resistances in series: aqueous diffusional barrier and lipoidal membrane. Even if partitioning into the membrane and membrane diffusion are both enhanced for lipophilic compounds, the absorption rate constant is limited by the aqueous diffusion. To estimate the influence of structural modifications on each property and to establish the role of lipophilicity in controlling in situ absorption and in vitro antibacterial activity, the PATQSAR search system is used to construct structure-property relationships. The structural models, which explain 99% of the total variance of each physicochemical property and 96% of each in vitro biological activity, provide an explicit and precise interpretation of lipophilicity, absorption, and antimicrobial activity. The results confirm the important role of lipophilicity in controlling absorption, as pointed out by the biophysical model for the piperazinyl series, and suggest the introduction of electronic factors in order to extend the model to heterologues. They also justify the mechanism by which quinolones are assumed to induce antibacterial activity.

Algorithms↗
PubMedDate not supplied

Evidence of efflux-mediated and saturable absorption of rifampicin in rat intestine using the ligated loop and everted gut sac techniques.

This study was carried out to explore whether efflux-mediated and saturable mechanisms play any role toward poor and variable intestinal absorption of rifampicin. In situ segmental permeability of rifampicin at various residence times was determined in rat gastrointestinal tract using the ligated loop technique. The involvement of efflux-mediated and saturable absorption of rifampicin was studied in rat intestine using the everted sac method. The samples were analyzed by a validated HPLC method. Rifampicin showed decreased permeability in jejunum and ileum with an increase in residence time. The permeation of rifampicin from the serosal to the mucosal side (secretion) was significantly higher than permeation from the mucosal to the serosal side (absorption) of jejunum and ileum. This indicated the involvement of efflux-mediated transport. Addition of verapamil, an inhibitor for P-glycoprotein (Pgp), multidrug resistance associated protein-2 (MRP-2), and other related transporters, increased absorption of rifampicin in jejunum and ileum by 2-3-fold and decreased secretion by almost 4-fold. The permeation rate (flux) of rifampicin through duodenum increased with concentration up to 300 microg/mL, becoming constant thereafter, indicating the existence of saturable absorption. There was no saturable permeation in jejunum and ileum. Thus the present study indicates the involvement of efflux-mediated and saturable absorption mechanisms of rifampicin in rat intestine, which act as barriers to the absorption of the drug. This explains the drug's poor absolute bioavailability. As Pgp varies from person to person to an extent of 2-8-fold, it can be one direct reason for the interindividual variable bioavailability shown by rifampicin.

Animals↗
PubMed2001

Mutual inhibition of the insulin absorption-enhancing properties of dodecylmaltoside and dimethyl-beta-cyclodextrin following nasal administration.

PURPOSE: To determine if a nasal insulin formulation containing two distinct absorption-enhancing agents exhibits an additive or synergistic increase in the rate of systemic insulin absorption. METHODS: The pharmacokinetics and pharmacodynamics of insulin absorption were measured in hyperglycemic anesthetized rats following nasal insulin administration with formulations containing two different types of absorption-promoting agents, dimethyl-beta-cyclodextrin (DMBCD) and dodecylmaltoside (DDM). RESULTS: When either DDM (0.1-0.5%) or DMBCD (1.0-5.0%) was added to the nasal insulin formulation, a significant and rapid increase in plasma insulin levels was observed, with a concomitant decrease in blood glucose concentration. A combined preparation containing 0.25% DDM (0.005 M) and 2.5% DMBCD (0.019M), however, failed to cause an increase in plasma insulin levels or a decrease in blood glucose concentration. Increasing concentrations of DDM added to an insulin formulation with a fixed DMBCD concentration caused a decrease, rather than an increase, in systemic absorption of insulin. CONCLUSIONS: Mixing DMBCD and DDM resulted in mutual inhibition of their ability to enhance systemic absorption of insulin following nasal delivery. The results are consistent with the formation of an inclusion complex between DDM and DMBCD which lacks the ability to enhance nasal insulin absorption.

Absorption↗
PubMed1998

Use of the InteliSite capsule to study ranitidine absorption from various sites within the human intestinal tract.

PURPOSE: The purpose of this study was to evaluate the extent of ranitidine absorption from an externally activated drug-delivery system in two distinct regions of the intestine (jejunum and ileum) in healthy human volunteers. This investigation also was designed to evaluate the utility of the InteliSite capsule for studying regional intestinal drug absorption in humans. METHODS: The intestinal absorption of ranitidine from the jejunum and ileum was compared in eight, healthy volunteers in this open-label, two-way crossover study. In two of the eight volunteers, absorption from the colon also was studied. Subjects swallowed the capsule containing ranitidine solution (121 mg) and 100 microCi of 99mTc-DTPA. The endcap of the capsule contained 20 microCi of (111)In-DTPA. At the desired intestinal site, the capsule was activated by the application of an external RF magnetic signal (6.78 MHz operating frequency) and the ranitidine solution was released. Blood samples were collected from a forearm vein for 12 hours after capsule activation. RESULTS: The capsule released the ranitidine solution when activated in the jejunum, ileum and colon (visualized by the gamma camera). There was no difference in the extent of ranitidine absorption or ranitidine pharmacokinetics when the capsule was activated in the jejunum or ileum. CONCLUSIONS: This study demonstrates the utility of a novel, externally activated drug-delivery system to assess site-specific intestinal drug absorption in humans. Results indicate that use of the InteliSite capsule method to evaluate site-specific intestinal ranitidine absorption in humans yields data similar to that obtained previously by means of oral intubation studies.

Adult↗
PubMed1998

Nitric oxide donors enhance rectal absorption of macromolecules in rabbits.

PURPOSE: The objective of this investigation is to evaluate the potential of nitric oxide (NO) donors as a new class of absorption enhancers which may act on intestinal epithelial cells through epithelial actions of the chemical mediator, NO. METHODS: Suppositories containing NO donors and insulin were administered into the rabbit rectum. After administration of the suppository, blood samples were collected from the auricular vein. The plasma insulin and glucose concentrations were determined. RESULTS: The NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP, 4 mg) induced a significant increase in the rate of insulin absorption from the rectum. Administration of a suppository containing SNAP without insulin affected neither the plasma insulin nor the plasma glucose concentration. Other NO donors, NOR1 and NOR4, also induced increases in the insulin absorption. The absorption enhancement effect of SNAP was inhibited by coadministration of the NO scavenger carboxy-PTIO. SNAP also enhanced FITC-dextran (MW 4,000) absorption. Little cytotoxicity of SNAP (3.0 mg/ml) as assessed in terms of the rate of lactate dehydrogenase (LDH) release from Caco-2 cells was detected for 2 h of incubation. CONCLUSIONS: These findings suggest that NO enhanced macromolecular absorption from the rectum without mucosal cell damage, and that NO donors can act as potent absorption enhancers.

Animals↗
PubMed1997

Improved prediction of in vivo peroral absorption from in vitro intestinal permeability using an internal standard to control for intra- and inter-rat variability.

PURPOSE: To evaluate the use of an in vitro intestinal permeability model to predict rat and human absorption as well as to evaluate the use of an internal standard to control for intra- and inter-rat variability. METHODS: In vivo peroral absorption and in vitro steady-state intestinal permeability coefficients were determined in the rat for a variety of structurally different compounds with different physicochemical properties including: progesterone, hydrocortisone, salicylic acid, caffeine, clonidine, p-aminoclonidine, UK-14304, oxymetazoline, mannitol, PEG 900, PEG 4000, and a number of novel hydrophilic chemical entities. RESULTS: The intestinal permeability coefficients determined in vitro could be used to predict the peroral absorption of a compound in both the rat and human. Normalizing the permeability of a test compound to an internal standard, e.g. mannitol, greatly improved the prediction of peroral absorption. CONCLUSIONS: The use of an internal standard can aid in the prediction of the peroral absorption of a test compound, in particular, for one that has moderate absorption in the range of 20-80%. Moreover, these methods would appear to be a useful means to improve the prediction of other absorption models as well, such as the Caco-2 cell systems and in-situ perfusion methods.

Administration, Oral↗
PubMed1989

Enhanced intestinal absorption of cyclosporine in rats through the reduction of emulsion droplet size.

The intestinal absorption of cyclosporine was measured in situ in rats using an olive oil emulsion prepared by either stirring or homogenization. The surface area of the homogenized dosage form was twice that of the stirred dosage form. The apparent permeability of cyclosporine from the homogenized emulsion was about twice that of the emulsion prepared by stirring. The examination of absorption in different intestinal segment lengths suggested the presence of an "absorption window." The absorption of cyclosporine appeared to be concentration independent and, therefore, non-carrier mediated. The dependence of absorption upon the intestinal perfusion rate suggested that the stagnant aqueous layer is the rate-limiting barrier in cyclosporine absorption. These results indicate that the bioavailability of cyclosporine administered in an emulsion can possibly be increased by enhancing its rate of absorption through the reduction of droplet size.

Animals↗
PubMed1996

In vivo and in vitro percutaneous absorption of cancer preventive flavonoid apigenin in different vehicles in mouse skin.

PURPOSE: In vivo and in vitro percutaneous absorption of apigenin was investigated in three vehicles previously used in cancer prevention studies to determine the drug delivery properties for optimal chemo-preventive activity. METHODS: In vivo percutaneous absorption of apigenin on SENCAR mice was studied with DMSO and acetone/DMSO (A/D, 4:1) vehicle. In vitro percutaneous absorption studies used whole mouse skin, without subcutaneous fat, mounted on Franz diffusion cells with 37 degrees C Dulbecco's phosphate-buffered saline as the receptor fluid. The skin was treated with [G-3H]-apigenin in DMSO, A/D (4:1), or propylene glycol/DMSO (PG/D, 4:1). RESULTS: Apigenin uptake by epidermal cells and distribution in epidermis following in vivo topical treatment in two vehicles was in the order of A/D > DMSO, while apigenin distribution in dermis and subcutaneous fat was not different between DMSO and A/D. Total apigenin absorption in mouse skin in vitro was in the order of A/D > DMSO > PG/D. However, apigenin sub-tissue distribution within epidermis determined by tape-stripping and by determination of apigenin in dermal and epidermal tissue indicated that DMSO delivered more apigenin into viable epidermis than A/D while A/D deposited more apigenin in the stratum corneum. Apigenin absorption in mouse skin with DMSO or A/D showed saturation kinetics while apigenin in PG/D showed very low absorption initially and non-saturated absorption in a period of 6 hr. HPLC-scintillation profiles of in vitro samples showed no evidence of apigenin metabolism in mouse skin. CONCLUSIONS: Delivering apigenin into viable epidermis appears to be a necessary property for an apigenin formulation to be effective in skin cancer prevention.

Acetone↗