Intact Rat Skin Research Articles

Acute toxicity of a combined fipronil and pyriproxyfen shampoo

The purpose of the research is to study the acute oral and dermal toxicity of a veterinary drug (fipronil, pyriproxyfen) in mice and rats.Materials and methods. The studies were performed according to the Methodical Guidelines of the State Pharmacological Committee in the vivarium of the VNIIP – FSC VIEV from February to April 2021. White outbred male mice and male rats were used as a test system to study toxicological characteristics of the study drug. The veterinary drug Insektal Shampoo is a topical solution that contains fipronil and pyriproxyfen as active ingredients. In studying the acute oral toxicity and acute dermal toxicity of the study drug on laboratory animals, established procedures were used.Results and discussion. The median lethal dose (LD50) was 12 500 (11,532÷13,468) mg/kg when administered to the white male mice intragastrically as per Miller-Tainter method. According to the generally accepted hygiene classification, the drug was classified as hazard class 4 according to GOST 12.1.007-76. For the white male rats, LD50 was more than 20,800 mg/ kg (hazard class 4). When applied to intact rat skin, LD50 was more than 10 400 mg/kg, which corresponds to hazard class 4.

Karyometric Parameters of Skin Fibroblasts in the Early Stages of Wound Healing

The aim of the study was a comparative study of the karyometric parameters of fibroblasts using various acid-modified solutions in the early stages of healing of skin wounds in rats.Material and methods. The experiment was carried out on 75 Wistar rats. For the treatment of wounds, 0.9% NaCl solution was used at a pH of 5.0; 7.0; and 7.5. The material was fixed in Shtiva liquid, 10% formalin solution. Thin paraffin sections (4–5 μm) were stained with hematoxylin and eosin, azan according to Heidenhain. The area of fibroblast nuclei was determined planimetricallyResults. Three types of fibroblasts were found in the skin of intact rats. The papillary layer contained papillary fibroblasts; the reticular layer – reticular fibroblasts. The third type of fibroblasts was located between the hair follicles. In rats of all experimental groups, on the 1st day after the wound was inflicted, extensive inflammatory processes, hemorrhages, and necrotic changes in the structural components of the skin were revealed. On the 3rd day after the wound was inflicted in rats of the 1st and 4th groups, the area of the nuclei of papillary fibroblasts in the peripheral areas of the wound statistically significantly increased by 24.4% and 22.4%, respectively, compared with the control. In animals of the 3rd group, the area of fibroblast nuclei remained unchanged. On the 5th day, an increase in the number of fibroblasts over the entire surface of the wound was observed in rats of all experimental groups. The area of fibroblast nuclei in rats of the 4th group increased statistically significantly by 26.5% (Р<0.001) as compared to the control. In animals of the 3rd group, the increase in the area of the nuclei in comparison with the control was only 6.5%, while no statistically significant changes were found in comparison with the control. The area of the fibroblast nuclei located between the hair follicles reached a maximum value, which indicated a high functional tension of the hair follicle fibroblasts. Conclusion. The use of 0.9% NaCl solution with pH 5.0 in the first phase of wound healing and 0.9% NaCl solution with pH 7.5 in the second phase of wound healing reduces inflammation processes, while the secretory activity of fibroblasts increases, and collagenization is accelerated.

Histamine augments collagen content via H1 receptor stimulation in cultures of myofibroblasts taken from wound granulation tissue

The inflammatory reaction influences the deposition of collagen within wound granulation tissue. The aim of the present study is to determine whether histamine acting directly on myofibroblasts derived from wound granulation tissue may influence collagen deposition. It also identifies the histamine receptor involved in this process. The experiments were carried out on cells isolated from the granulation tissue of a wound model (a polypropylene net inserted subcutaneously to rats) or intact rat skin. Collagen content was measured following the addition of different concentrations of histamine and treatment with histamine receptor antagonists (ketotifen – H1 inhibitor, ranitidine – H2 inhibitor) and a histamine receptor H1 agonist (2-pyridylethylamine dihydrochloride).The cells were identified as myofibroblasts: alpha-smooth muscle actin, vimentin, and desmin positive in all experimental conditions. Histamine increased the collagen level within both cell cultures, i.e., those isolated from granulation tissue or intact skin. It did not, however, influence the expression of either the collagen type I or III genes within the cultured myofibroblasts. Histamine activity was reduced by ketotifen (the H1 receptor inhibitor) and increased by the H1 receptor agonist, as demonstrated by changes in the levels of collagen in the myofibroblast culture. Histamine increased collagen content within the cultures, acting directly on myofibroblasts via H1 receptor stimulation.

ACUTE CUTANEOUS TOXICITY AND IRRITANT EFFECTS OF IVERMECTIN FOR EXTERNAL USE IN WHITE RATS

In All-Russian Scientific Research Institute for Fundamental and Applied Parasitology of Animals and Plant – a branch of the Federal State Budget Scientific Institution "Federal Scientific Centre VIEV" a prototype of a new drug form of Ivermectin was developed for cutaneous use against endo- and ectoparasites. The dosage form is a transparent solution for application to the skin with an Ivermectin content of 0.5%. For the experiment, 18 white male rats weighing 180-200 g were selected, which were divided into 2 experimental and one control group of 6 heads each. The coat of all animals was shaved on the back with an area of about 5x5 cm. The drug was applied at doses of 5 000 and 10 000 mg / kg, the control group did not receive the drug. The LD50 of the Ivermectin dosage form is more than 10 000 mg / kg, according to GOST 12.1.007-76 the drug belongs to the 4th class of danger when applied to the skin. The drug does not have an irritating effect when applied once to intact rat skin.

Topical fentanyl stimulates healing of ischemic wounds in diabetic rats.

Topically applied opioids promote angiogenesis and healing of ischemic wounds in rats. We examined if topical fentanyl stimulates wound healing in diabetic rats by stimulating growth-promoting signaling, angiogenesis, lymphangiogenesis and nerve regeneration. We used Zucker diabetic fatty rats that develop obesity and diabetes on a high fat diet due to a mutation in the Leptin receptor. Fentanyl blended with hydrocream was applied topically on ischemic wounds twice daily, and wound closure was analyzed regularly. Wound histology was analyzed by hematoxylin and eosin staining. Angiogenesis, lymphangiogenesis, nerve fibers and phospho-platelet derived growth factor receptor-β (PDGFR-β) were visualized by CD31-, lymphatic vessel endothelium-1, protein gene product 9.5- and anti-phospho PDGFR-β-immunoreactivity, respectively. Nitric oxide synthase (NOS) and PDGFR-β signaling were analyzed using Western immunoblotting. Fentanyl significantly promoted wound closure as compared to phosphate-buffered saline (PBS). Histology scores were significantly higher in fentanyl-treated wounds, indicative of increased granulation tissue formation, reduced edema and inflammation, and increased matrix deposition. Fentanyl treatment resulted in increased wound angiogenesis, lymphatic vasculature, nerve fibers, nitric oxide, NOS and PDGFR-β signaling as compared to PBS. Phospho-PDGFR-β co-localized with CD31 co-staining for vasculature. Topically applied fentanyl promotes closure of ischemic wounds in diabetic rats. Increased angiogenesis, lymphangiogenesis, peripheral nerve regeneration, NO and PDGFR-β signaling are associated with fentanyl-induced tissue remodeling and wound healing.

Effect of ethanol concentration in receiver fluid on in vitro transdermal test

The present paper was designed to investigate the effect of varying concentrations of ethanol in receiver solution on the in vitro transdermal permeation of drug across the rat skin. 5-fluorouracil (5-FU) was used as the model drug on account of its good hydrophility, the excised rat skins were treated with different concentration ethanol prepared with normal saline for 12 h, then replaced by normal saline and added the saturated model drug into the donor compartment to determine the transdermal parameters of the drug. Meanwhile, scanning electron microscopy (SEM) was employed to monitor the effect of the different concentration ethanol on the stratum corneum of the rat skin. The ethanol below the concentration of 15% didn't significantly affect the barrier profile of the rat skin, while significant difference of in steady-state transdermal rate and lag times were observed when the concentration of ethanol was 20% or above. The SEM studies indicated that wrinkle of the intact rat skin gradually disappeared and a number of flakes were desquamated from the skin when the concentration of ethanol was above 20%. The results showed that the low concentration of the ethanol (below 15%) didn't obviously affect the excised skin, yet the barrier profile of rat skin would significantly disrupted with the concentration of ethanol above 20%.

Low level laser therapy (AlGaInP) applied at 5J/cm2 reduces the proliferation of Staphylococcus aureus MRSA in infected wounds and intact skin of rats*

BACKGROUNDLaser therapy is a low cost, non-invasive procedure with good healing results. Doubts exist as to whether laser therapy action on microorganisms can justify research aimed at investigating its possible effects on bacteria-infected wounds. OBJECTIVETo assess the effect of low intensity laser on the rate of bacterial contamination in infected wounds in the skin of rats. METHODSAn experimental study using 56 male Wistar rats. The animals were randomly divided into eight groups of seven each. Those in the "infected" groups were infected by Staphylococcus aureus MRSA in the dorsal region. Red laser diode (AlGaInP) 658nm, 5J/cm2 was used to treat the animals in the "treated" groups in scan for 3 consecutive days. Samples were drawn before inoculating bacteria and following laser treatment. For statistical analysis we used the nonparametric Wilcoxon (paired data) method with a significance level of p <0.05. RESULTSThe statistical analysis of median values showed that the groups submitted to laser treatment had low bacterial proliferation. CONCLUSIONThe laser (AlGaInP), with a dose of 5J/cm2 in both intact skin and in wounds of rats infected with Staphylococcus aureus MRSA, is shown to reduce bacterial proliferation.

Measurement of Skin Permeation/Penetration of Nanoparticles for Their Safety Evaluation

The aim of the present study was to quantitatively evaluate the skin permeation/penetration of nanomaterials and to consider their penetration pathway through skin. Firstly, penetration/permeation of a model fluorescent nanoparticle, Fluoresbrite®, was determined through intact rat skin and several damaged skins. Fluoresbrite® permeated through only needle-punctured skin. The permeation profiles of soluble high molecular compounds, fluorescein isothiocyanate-dextrans (FITC-dextrans, FDs), with different molecular weights were also measured for comparison. The effects of molecular sizes and different skin pretreatments on the skin barrier were determined on the skin penetration/permeation of Fluoresbrite® and FDs. Fluoresbrite® was not permeated the intact skin, but FDs were permeated the skin. The skin distribution of titanium dioxide and zinc oxide nanoparticles was also observed after topical application of commercial cosmetics. Nanoparticles in sunscreen cosmetics were easily distributed into the groove and hair follicles after their topical application, but seldom migrated from the groove or follicles to viable epidermis and dermis. The obtained results suggested that nanoparticles did not permeate intact skin, but permeated pore-created skin. No or little permeation was observed for these nanomaterials through the stratum corneum.

Investigating effect of microemulsion components: In vitro permeation of ketoconazole

The purpose of this study was to evaluate the effect of oil, surfactant/co-surfactant mixing ratios and water on the in vitro permeation of ketoconazole (KTZ) applied in O/W microemulsion vehicle through intact rat skin. Lauryl Alcohol (LA) was screened as the oil phase of microemulsions, due to a good solubilizing capacity of the microemulsion system. The pseudo-ternary phase diagrams for microemulsion regions were constructed using LA as the oil, Labrasol (Lab) as the surfactant (S) and ethanol (EtOH) as the cosurfactant (CoS). The formulation which showed a highest permeation rate of 54.65 ± 1.72 µg/cm2/h1 and appropriate physico-chemical properties was optimized as containing 2% KTZ, 10% LA, 20% Lab/EtOH (1:1) and 68% double distilled water (w/w). The efficiency of microemulsion formulation in the topical delivery of KTZ was dependent upon the contents of water and LA as well as Lab/EtOH mixing ratio. It was concluded that the percutaneous absorption of KTZ from microemulsions was enhanced with increasing the LA and water contents, and with decreasing the Lab/EtOH ratio in the formulation. Candida albicans was used as a model fungus to evaluate the antifungal activity of the best formula achieved, which showed the widest zone of inhibition as compared to KTZ reference. The studied microemulsion formulation showed a good stability for a period of three months. Histopathological investigation of rat skin revealed the safety of microemulsion formulations for topical use. These results indicate that the studied microemulsion formulation might be a promising vehicle for topical delivery of KTZ.

Imaging dermal blood flow through the intact rat skin with an optical clearing method

Noninvasive detection of skin microcirculation is very significant for clinical diagnosis and therapy of peripheral vascular disease. In this study, an optical clearing method enables a laser speckle contrast imaging (LSCI) technique to image dermal blood flow through intact rat skin. The optical clearing effect of rat skin in vitro caused by a mixture of PEG-400 and Thiazone is evaluated by a commercially available spectrophotometer with an integrating sphere. A LSCI system is applied to image the dermal blood flow of in vivo rat skin after topical treatment of the agents. The results show that the reduced scattering coefficient (630 nm) is down to 60% of the initial value after 40 min of topical treatment of the mixture on skin in vitro. In vivo experimental results show that a 12-min treatment of the mixture on the epidermis can make the skin transparent and dermal vessels can be observed, while treatment with pure PEG-400 cannot. The process of skin optical clearing lasts, and the skin can be recovered by treatment of saline solution. Because optical clearing decreases the temporal contrast, dermal blood flow can be obtained by the laser speckle contrast imaging technique.

Percutaneous penetration of uranium in rats after a contamination on intact or wounded skin

The aim of this work is to assess in vivo in a hairless rat model, the percutaneous diffusion of uranium through intact or wounded rat skin. Six types of wounds were simulated by excoriation and burns with 10 N HF, 2, 5 and 14 N HNO3 and 10 N NaOH on anaesthetised hairless rats. Percutaneous penetration through wounded skin towards blood and subsequent urinary excretion of uranium was followed in vivo during 24 h. The influence of the physicochemical form (solution or powder) of uranyl nitrate (UN) on its percutaneous diffusion was also investigated. UN, even as a powder, can diffuse through intact skin. The presence of uranium in blood is more persistent and its urinary elimination is slower after an HF burn than after an HNO3 burn. Excoriation increases dramatically percutaneous absorption of UN. Thus, percutaneous diffusion of UN is largely dependent on skin barrier integrity with a particular importance of stratum corneum.

Invitro Release Study of Sodium Salicylate from Lecithin Based Phospholipid Microemulsions

Sodium salicylate containing microemulsions have been formulated, based on the previous phase diagram studies, using a pharmaceutically acceptable surfactant and oil. The effects of formulation variables on the release profile of the drug from microemulsion through intact rat skin were also determined experimentally. In this investigation, two commercially available lecithins (namely Epikuron 200 and Epikuron 170), three short chain alcohols (n-butanol, isopropanol and n-propanol) and isopropyl myristate (IPM) were used as surfactant, cosurfactant and oil, respectively. The water phase was composed of sodium salicylate solution (2% w/v). To investigate the release profile, samples with 25% wt% total surfactant content were prepared with different surfactant/cosurfactant weight ratios (Km of 1:1 and 1.5:1) and various amounts of drug solution (from 7 to 35 wt%), depending on the nature of alcohol. Two compartment Franz diffusion cells, equipped with rat skin as the absorption membrane, were employed for release studies. All experiments were performed at room temperature and sampling was taken over 12 hours with one-hour intervals. The amount of drug released was determined spectrophotometrically and the permeation parameters were then calculated. Results showed that systems formulated with 7 and 9% drug solution, were not capable of releasing the drug with a lower rate, compared to the corresponding drug solutions, while in other systems, a lower release rate was observed in comparison to the control samples. In general, among the systems investigated, those prepared with n-propanol at Km of 1.5:1 and 11-20 wt% and 29% dispersed phase showed a relatively lower absorption rate, comparing to the corresponding control samples , regardless of the nature of surfactant and cosurfactant. Under passive conditions, the flux from microemulsions followed the zero order behavior with respect to the donor concentration.

Especially Polymorphonuclear Leukocytes, but also Monomorphonuclear Leukocytes, Roll Spontaneously in Venules of Intact Rat Skin: Involvement of E-Selectin

White blood cells roll spontaneously in venules of intact, noninflamed rat skin. We investigated noninvasively in two experimental series which leukocyte subtypes participate in this phenomenon and the possible involvement of E-selectin. Male Lewis rats were anesthetized with sodium pentobarbital, and intravital video microscopy was performed on postcapillary venules in the nail-fold of a hind leg. In series 1 acridine yellow was infused for 15 min (50 mg per kg intravenously) to stain the leukocyte nuclei in situ. With the use of fluorescence microscopy rolling leukocytes could be classified unequivocally as polymorphonuclear (granulocytes) or monomorphonuclear (lymphocytes/monocytes) by the shape of their nucleus. Irrespective of vessel depth beneath the skin surface (25-45 microm), most identified rolling leukocytes were classified as granulocytes (72%-100%; median 89%). This percentage was independent of total rolling leukocyte flux, systemic leukocyte count, or their in vitro differentiation pattern. In series 2, rats were treated with either a synthetic, highly selective E-selectin blocking peptide or a control peptide (intravenously, 12 mg peptide per kg bolus, followed by 50 mg per kg per h). E-selectin blockade significantly reduced the leukocyte rolling level to about 50% of baseline (p <0.01), whereas the rolling velocity increased (p <0.01); the control peptide had no effect. In summary, most of the leukocytes rolling spontaneously in postcapillary venules of intact rat skin are granulocytes, despite the absence of an acute inflammatory reaction. One of the adhesion molecules involved in this phenomenon is E-selectin.

Early Steps of Insulin Action in the Skin of Intact Rats

Insulin is an important regulator of growth and initiates its action by binding to its receptor, which undergoes tyrosyl autophosphorylation and further enhances its tyrosine kinase activity towards other intermediate molecules, including insulin receptor substrate 1, insulin receptor substrate 2, and Shc. Insulin receptor substrate proteins can dock various src-homology-2-domain-containing signaling proteins, such as the 85 kDa subunit of phosphatidylinositol 3 kinase and growth-factor-receptor-bound protein 2. The serine-threonine kinase is activated downstream to phosphatidylinositol 3 kinase. Shc protein has been shown to directly induce the association with growth-factor-receptor-bound protein 2 and downstream the activation of the mitogen-activated protein kinase. In this study we investigated insulin signal transduction pathways in skin of intact rats by immunoprecipitation and immunoblotting with specific antibodies, and also by immunohistochemistry with anti-insulin-receptor antibody. Our results showed that skin fragments clearly demonstrated the presence of insulin receptor in cell bodies of the epidermis and hair follicles and some faint staining was also detected in fibroblasts of the dermis. It was also observed that acute stimulation with insulin can induce tyrosyl phosphorylation of insulin receptor, that the insulin receptor substrates and Shc proteins serve as signaling molecules for insulin in skin of rats, and that insulin is able to induce association of insulin receptor substrate 1/phosphatidylinositol 3 kinase and Shc/growth-factor-receptor-bound protein 2 in this tissue, as well as phosphorylation of mitogen-activated protein kinase and serine-threonine kinase, demonstrating that proteins involved in early steps of insulin action are expressed in skin of intact rats and are quickly activated after insulin stimulation.

Water permeation barrier in isolated cutaneous newborn rat epidermis

Abnormal water barrier function occurs in irritated skin and certain cutaneous diseases. Methods have been compared for separating the epidermis (site of the barrier) from the whole skin without disturbing the barrier function. The epidermis was separated from newborn rat skin by (1) exposure to 10% trypsin at 4° C for 16 h, (2) exposure to 0.2% dispase at 4° C for 16 h, (3) heating for 50 s at 55° C, (4) or heating for 40 s at 50° C after the whole skin was kept in medium at the air–liquid interface for 1 day at 35° C. Water permeation of the isolated epidermis was then measured immediately or after 3, 5, 8, and 10 days of maintenance at the air–liquid interface. The water permeation barrier constant (k p) was 1.9 ± 0.9 cm/h in intact rat skin. At 0 day of maintenance, the k p of the epidermis was 2.1 ± 0.9 after treatment with trypsin, 3.8 ± 1.2 after dispase, and 4.3 ± 1.4 after immediate heating, or 2.2 ± 0.7 cm/h after culture and heating. The dispase and heating methods disrupted the barrier to a greater extent than did the trypsin and culture-heating methods. The latter two methods allowed the k p to be maintained at low levels for 8 days (k p for trypsin 2.8 ± 0.9 and 2.5 ± 0.8 for culture-heating). Epidermis isolated by the trypsin or culture-heating techniques and maintained at the air–liquid interface can be used to study the mechanism by which barrier function is disrupted by chemicals.

Levels of plasma C19 steroids and 5 alpha-reduced C19 steroid glucuronides in primates, rodents, and domestic animals.

In this study, a comparison of circulating levels of androsterone glucuronide and androstane-3 alpha, 17 beta-diol glucuronide in the male and female of several mammalian species was performed. Glucuronidated steroids were not detected in the circulation of the dog, bovine, swine, and rodent. High levels of circulating glucuronidated steroids were measured in the cynomolgus monkey and found to be 10-fold higher than in humans. The determination of tissue levels of unconjugated and conjugated C19 steroids was then performed in intact and castrated rats treated with androgens. Steroid glucuronides were not detected in the plasma, skin, prostate, or liver of either intact or treated rats, although the levels of unconjugated steroids in the plasma and tissues were increased after steroid treatments. Significant levels were detected in the bile, thus suggesting hepatic formation of steroid glucuronides in the rat. It is suggested that the monkey represents the best animal model to date to study the contribution of diphosphoglucuronosyltransferases present in steroid target peripheral tissues to circulating levels of steroid glucuronides.

Keratinized epithelial transport of beta-blocking agents. II. Evaluation of barrier property of stratum corneum by using model lipid systems.

Model lipid mixtures composed of ceramide (40%), cholesterol (25%), palmitic acid (25%) and cholesterol 3-sulfate (10%) were used as the model for intercellular lipids of stratum corneum (SC) to evaluate a barrier function of SC for drug permeation. Six beta-blockers, propranolol, metoprolol, timolol, pindolol, nadolol and atenolol, were used as the model permeants. The maximum flux values (observed flux/thermodynamic activity, Jmax) of drugs through the membrane coated with the model lipid mixtures and two keratinized membranes, rat skin and hamster cheek pouch, were determined in vitro using a Franz-type diffusion cell. Further, drug partition coefficients to the multilamellar liposomes prepared by the model lipid mixtures were determined. The Jmax values obtained in the model lipid-coated membrane, in the intact rat skin and in the intact hamster cheek pouch mucosa, bore a linear relationship to each other. These results suggest that the model lipid-coated membrane is a useful tool for the prediction of the drug permeability through the keratinized membrane in the in vitro system. The Jmax values also correlated with drug partition to the model lipid liposomes, suggesting the validity of the use of the model lipid mixtures as the substitutes for the intercellular lipids of the stratum corneum.

Role of prostanoids in the inflammatory reaction and their therapeutic potential in the skin.

Vasodilatory prostaglandins (PG), contributing to the inflammatory reaction, have gained considerable attention. It is becoming apparent that PG have pharmacological effects traceable to biological activities distinct from smooth muscle relaxation. The data from pharmacological experiments presented here indicate the diverse action of vasodilatory PG analogues in the skin of laboratory animals. Nocloprost, a stable PGE2 analogue, induced erythema in intact skin of rats when applied topically and inhibited in the same dose range an irritant-induced inflammatory reaction in the ears of mice. Iloprost, a stable PGI2 analogue, showed proinflammatory activity after local application by enhancing the leukotriene B4 induced cell infiltration in the skin of mice. The attenuation of the spreading of ear necrosis in mice, on the other hand, indicates an anti-ischemic therapeutic potential of iloprost. Research in the past has elucidated the influence of PG on the vascular component of inflammation, but the role of PG on the cellular component of inflammation is less clear. The diverse effects of PG in skin indicate the need for a better understanding of their local actions.

Keratinized epithelial transport of beta-blocking agents. I. Relationship between physicochemical properties of drugs and the flux across rat skin and hamster cheek pouch.

The maximum fluxes (Jmax) of beta-blockers through keratinized membranes were determined in vitro and compared with their physiochemical parameters such as lipophilicity (log k'0) and melting point (mp). Rat abdominal skin and hamster cheek pouch mucosa were used as the model membranes. Propranolol, metoprolol, timolol, pindolol, nadolol and agenolol were used as beta-blockers with a variety of physicochemical characters. Linear relations of Jmax with either log k'0 or mp were observed both in intact rat skin and in intact hamster cheek pouch, suggesting that the lipophilicity and thermodynamic activity of a drug in the crystal state primarily affect the drug's permeation through these membranes. However, the slope, dJmax/d(log k'0), for cheek pouch mucosa was greater than that for rat skin, corresponding to the lack of appendigeal shunt pathways in cheek pouch. Penetration studies using the delipidized membranes and the isolated stratum corneum sheet of hamster cheek pouch mucosa clarified that the primary rate-limiting barrier function might exist in the lipid layer of the stratum corneum. Jmax values for the tape-stripped and delipidized skins correlated with both the solubilities of drugs in the vehicle and with the mp, suggesting the polar porous characteristics of both model membranes. However, a theoretical approach confirmed that the contribution of an intracellular or aqueous pore route in the intact membrane to the permeation of drugs with positive lipophilic indexes is negligible.

Studies on the Metabolic Fate of Betamethasone Butyrate Propionate. (IV). Absorption, distribution and excretion in rats and rabbits.

3H-BBPをラットおよびウサギに0.25mg/kgで経皮(非密封法)，あるいは1mg/kgで皮下投与し，その吸収，分布，排泄について検討し，以下の結果を得た．1．軟膏またはクリームを正常皮膚動物に経皮投与した際，全身系への経皮吸収率は雄性ラットでは約3～5%，雌性ラットでは約14%，また雄性ウサギでは約14%であった．損傷皮膚雄性ラットでは約30～50%であった．2．正常皮膚動物における血液または血漿中放射能濃度の最高到達時間および最高値は雄性ラット:24時間，0.6～0.8ng/ml，雌性ラット:8時間，4.7ng/ml雄性ウサギ:13時間，3.0ng/mlであった．また，損傷皮膚雄性ラットでは5時間，8.6～15.7ng/mlであった．3．主排泄経路はラットでは糞であったが，ウサギの尿糞中排泄率の割合はほぼ同じであった．4．正常皮膚雄性ラットにおける組織内放射能濃度は，投与後8時間あるいは24時間に最高濃度を示し，肝臓，腎臓副腎，貯精嚢および膀胱に高い濃度が認められた．各組織からの消失は緩慢であり，特に血液かbの消失が遅延した．塗布部皮膚のミクロオートラジオグラムより，BBPの経皮吸収経路として付属器官を経由するルートと経表皮ルートが確認された．5．正常皮膚雄性ラットに7回反復投与した際，毎回投与後24時間における血液および組織中放射能濃度は，投与回数に伴い上昇する傾向を示した．7回投与後の血液および組織中からの放射能の消失は緩慢であったが，7回投与後の尿および糞中排泄率は単回投与群と相違が認められなかった．6．妊娠ラットに3H-BBPを皮下投与した際の全身オートラジオグラムより，胎盤通過性が確認されたものの，放射能が胎仔組織に残留する傾向は認められなかった．