Rabbit ear test

In vivo alternative approaches to evaluating dermal toxicity are limited to one other dose site and two other species of small animals. These are the guinea pig, mouse ear, and rabbit ear tests. Gilman has previously presented a short overview of these three alternatives, but some additional information has since become available. 

Other animal tests have been used to study skin irritation by surfactants or other chemicals and have been reviewed by Gabriel [50]. They are the mouse ear swelling test, the guinea pig immersion technique, the cumulative irritation test on rabbits, and the rabbit ear test. As their usage is continually declining, the reader is referred to Ref. 50 for further details. 

Rabbit Ear Bioassay for Acnegenic Activity. Acnegenic activity of 2-7-DCDD, 1,2,3,4-TCDD, 2,3,7,8-TCDD, HCDD, and OCDD was tested by applying 0.1 ml of either a solvent solution or the supernatant of a solvent suspension of each compound to the inner surface of the rabbit s ears five days a week for four weeks. The ears were examined weekly for signs of chloracne, inflammation, and hyperkeratosis. The responses were divided into five categories (1) none, (2) very slight, (3) slight, (4) moderate, and (5) severe. 

Caldum channel antagonist activity was determined in isolated rabbit ear artery rings depolarized by a high K+ concentration [7]. The duration of action in vitro (Dw) was determined by means of wash-out experiments. Rabbit ear artery rings were contracted by a submaximal concentration of calcium, and incubated with the tested compounds for 60 min. Subsequently, they were washed with saline solution until the initial contraction was restored. Dw was defined as the time required by the tissue to recover the basal effect elicited by a submaximal concentration of calcium [8], Antihypertensive activity and Dw were determined in chronically implanted spontaneously hypertensive rats (SHR) [9]. 

Opdyke DL, Burnett CM (1965) Practical problems in the evaluation of the safety of cosmetics. Proceedings of the Scientific Section of the Toilet Goods Association 44 3 1 Opdyke D (1971) The guinea pig immersion test A 20 year appraisal. CFTA Cosmetic J 3 46—47 Phillips L, Steinberg M, Maibach HI, Akers WA (1972) A comparison of rabbit and human skin response to certain irritants. Toxicol Appl Pharmacol 21(3) 369-382 Uttley M, Van Abbe NJ (1973) Primary irritation of the skin Mouse ear test and human patch test procedures. J Soc Cosmet Chem 24 217-227... 

For testing the V. marginalis of the rabbit ear is used. Only water soluble drug substances should be administered. Each animal receives a volume of 0.2-0.5 ml of the solution into the mechanically congested ear vein. The ear on the other side is treated with the vehicle only. An alternative method is to use extra animals for treatment with the vehicle only. The speed of injection (volume per time) should be similar to the human clinical situation. During the injection and after the animals have to be observed for clinical signs. In total the animals have to be checked for a period of 14 days. The site of injection has to be checked for signs of local reactions. 

The test is conducted by using the mechanically congested A. centralis of the rabbit ear. The injection is directed into the distal direction. A 7,5 % solution of thiopental can serve as a positive control because it induces severe inflammatory reactions. The further procedure includes evaluation scores being used as for the i.v. injections. To eliminate the species-specific influence of small rodents (small artery) it is also recommended to use non-rodents like the dog. 

Over the years, several people have proposed a dermal irritation evaluation model based on the test material being applied to the inside surface of the rabbit ear. The advantages are that this site does not have to be shaved and the results may not over predict the toxicity as much. Seemingly no formal evaluation of a method based on this site has been performed and published. 

Phlebitis refers to inflammation of the vein wall. It can result in clinical symptoms such as pain and oedema, and can cause thrombus formation which may have serious consequences. Particulate matter is the most widely implicated cause of phlebitis. It is not surprising, therefore, that a link has been proposed between precipitation and phlebitis. The in vitro precipitation models described above may therefore be a good indicator of the phlebitic potential of a formulation. Phlebitis can be tested in vivo, usually by means of a rabbit ear vein model in which the test ear is visually compared with the control ear. 

The extensive toxicologic data available on TCDD and other dioxin and furan isomers from animal tests for rabbit ear chloracnegenicity, teratogenicity/fetotoxicity, reproductive toxicity, mutagenicity, clastogenicity, and carcinogenicity have been compiled and reviewed in previous publications ( , 2, 4). Because of space limitations... 

The vasoconstrictor action of shed blood tested by perfusion of the rabbit ear is markedly decreased by heparin and this was known long before the identification of the vasoconstrictor activity as serotonin (5-hydroxytryp-tamine). Heparin inhibits the release of both 5-hydroxytryptamine and a polypeptide from platelets into plasma, and in vitro there is mutual antagonism between heparin and 5-hydroxytryptamine . Heparin effectively antagonizes the effect of serotonin on pulmonary vascular bed and bronchial wall musculature and prevents the symptoms of 5-HT release in pulmonary embolism, in the cardiopulmonary by-pass, in experimental burn injuries and in carcinoid tumour. 

Some coumarin and chromone derivatives were considered to exert a protective action against irradiation [570]. However, recent experiments using the rabbit ear hole or guinea-pig wound-healing tests questioned the effectiveness of even the most potent compound, 0-(P4iydroxyethyl)rutoside [571]. 

Unless otherwise specified in the individual protocol, inject 10 ml of the test solution per kilogram of body weight into an ear vein of each of three rabbits, completing each injection within 10 min after the start of administration. The test solution is either the product, constituted if necessary as directed in the labeling, or the material under test. For pyrogen testing of devices or injection assemblies, use... 

Two weeks after the second injection, test bleed the rabbit from an ear vein. Swab the ear with xylene to dilate the vein before bleeding. 

The mixture is injected once a week for 3 weeks, and then the animal is maintained for 3 weeks without additional injections. Approximately 25-40 ml of blood is removed from the animal s ear vein to test for antibodies. One week after the first bleed the rabbit is boosted with half the antigen amount used earlier along with incomplete adjuvant incomplete adjuvant does not contain the mycobacteria. Serum is again removed 2 weeks after this injection and tested for antibody response. The enzyme-linked immunosorbent assay is used to determine if the titer (or antibody concentration) of the serum is sufficiently high to establish antibody binding to the antigen. This 3-week cycle is repeated as long as necessary to obtain the antibodies desired. 

Irritancy of local anesthetics after subcutaneous injections can be determined by subcutaneous injection into the ears of rabbits (Ulfendahl 1957). This method can be used not only as a screening selection criterion for finding an optimal local anesthetic but also as test method for evaluation of production batches (Hergott 1965). 

Rabbits of either sex weighing 2.5 to 3.5 kg are used. A volume of 0.1 ml of the test solution is injected in the outer part of the rabbit s ear avoiding hitting any blood vessels. The same volume of saline is injected into the contralateral ear. A pale discoloration of the skin appears immediately, which disappears within 1 h in the control. 

Viluksela M (1991) Characteristics and modulation of dithranol (anthralin)-induced skin irritation in the mouse ear model. Arch Dermatol Res 283(4) 262-268 Weil CS, Scala RA (1971) Study of intra- and interlaboratory variability in the results of rabbit eye and skin irritation tests. Toxicol Appl Pharmacol 19(2) 276-360... 

The discovery that exposure to exogenous chemicals could lead to cancer in humans was first made in the late 18th century, when Percival Pott demonstrated the relationship between cancer of the scrotum and the occupation of chimney sweepers exposed to coal tar/soot. Other examples noted later were scrotal cancers in cotton spinners exposed to unrefined mineral oils, and cancers of the urinary bladder in men who worked in textile dye and rubber industries due to their exposure to certain aromatic amines used as antioxidants. Experimental induction of cancer by chemicals was first reported in detail by Yamagiwa and Ichikawa in 1918, when repeated application of coal tar to the ear of rabbits resulted in skin carcinomas. Over the next few years, Kennaway and Leitch confirmed this finding and demonstrated similar effects in mice and rabbits from the application of soot extracts, other types of tar (e.g., acetylene or isoprene), and some heated mineral oils. These researchers also observed skin irritation sometimes accompanied by ulcers at the site of application of the test material. Irritation was thought to be an important factor in skin tumor development. However, not all irritants (e.g., acridine) induced skin cancer in mice and conversely, some purified chemicals isolated from these crude materials... 

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