Article: Validation of canine uterine and testicular arteries for the functional characterisation of receptor-mediated contraction as a replacement for laboratory animal tissues in teaching
PLoS ONE 15 (5): e0230516. https://doi.org/10.1371/journal. pone.0230516 May 26,2020 1
Louise Mulcahy, Elizabeth Tudor, Simon R. BaileyID*
Department of Veterinary Biosciences, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia
*Current address: Kinfauns Veterinary Centre, Little Clacton, Essex, UK
To validate the use of discarded canine testicular and uterine tissues to test drug-receptor interactions with the aim of replacing and reducing the use of tissues from laboratory animals.
Dogs are often used for drug design and testing in research and education. In veterinary schools for example, the use of tissues has involved the killing of the dogs for tissues such as vascular strips.
According to the researchers, utilising discarded tissues from routine surgical procedures, such as canine neutering, had not previously been investigated.
Agonist and antagonist drugs.
An agonist is a chemical that binds and activates the receptor to produce a specific biological response, whereas an antagonist blocks the action of the agonist and has an inverse agonist effect.
This study utilizes collected discarded tissues from routine surgical procedures, such as neutering, that have previously performed at an animal neutering clinic for stray dogs. The tissues were collected from healthy dogs of various ages and breeds. The dogs were not being used for research purposes, but were intended to be adopted after recovery from surgery.
Tissues were held in Krebs physiological solution and branches of the artery dissected from surrounding tissue. Drugs used in the experiment included alpha adrenoceptor agonists epinephrine (acting at both α1 and α2 receptors), phenylephrine (α1 selective) and UK14304 (α2 selective). Pre-treatment with the α1-selective antagonist, prazosin (10-8M or 10-7M), was also used. Serotonin (5-HT) receptor agonists were also used in the study, including 5-HT (acting at both 5-HT1 and 5-HT2 receptors), 5-carboxamidotryptamine (5-CT; 5-HT1 selective) and α-methyl 5-HT (5-HT2 selective). Stock solutions of each drug were produced by dissolving the drug in distilled water.
After a period of stabilization of resting tension, agonists were added in a cumulative manner. The tissues were allowed to reach maximum contraction for that agonist concentration, i.e. contract until a steady state was obtained, before the next concentration was added. For the antagonist experiments, the preparations were incubated with the antagonist for 10 mins before agonist concentrations were added to the bathing medium. Blood vessel segments from 4–6 individual animals were used for each treatment, and the effects of antagonists were examined on paired segments from the same animal.
Statistical analysis was performed on the data.
This study investigated the post-junctional α-adrenergic and 5-HT receptors mediating vasoconstriction in canine uterine and testicular arteries, in order to characterise the receptor populations to see how these blood vessels might be useful for teaching purposes. It demonstrated that the use of discarded tissues from routine neutering procedures is a valid and useful source of experimental tissue. According to the researchers, the amount of force generated by the muscular canine uterine and testicular arteries makes them superior tissues for teaching, with force generation of up to 12 and 8.8 grams tension, respectively.
Conclusion and Relevance
The researchers noted in the publication:
For the teaching of students in the biological sciences, pharmacology, veterinary or medical education programs, having the students observe first-hand the contraction of blood vessels and the effect of G protein-coupled receptor activation and blockade is a very valuable learning experience. These practical activities greatly enhance their understanding of the effect of different types of antagonists and other physiological modulators on the dose-response relationship to agonists. The use of these discarded canine tissues may replace the need to kill rodents, rabbits or guinea pigs to obtain the tissues necessary for these teaching practical classes.
In conclusion, the researchers also note that “This study has characterised the adrenergic and serotonergic receptors mediating vasoconstriction in canine uterine and testicular arteries. These results validate the use of discarded tissue from routine canine neutering procedures as a legitimate and effective tissue source for teaching, and there is promising potential for future application more widely”.
In the latest available reported animal use statistics (2017) compiled by HRA, a total of 11,308 dogs were used in research Australia wide. Of these numbers, 776 dogs were used in ‘teaching purposes’ in NSW and in Victoria 1587 were used in ‘educational objectives’.
HRA holds that dogs are NOT research and educational tools for use in the laboratory. This research publication shows that alternatives to the killing of animals can be explored and indeed be used.