title: Exercise induced stress in horses: selection of the most stable reference genes for quantitative RT-PCR normalization.
abstract: BACKGROUND
  Adequate stress response is a critical factor during athlete horses' training and is central to our capacity to obtain better performances while safeguarding animal welfare. In order to investigate the molecular mechanisms underlying this process, several studies have been conducted that take advantage of microarray and quantitative real-time PCR (qRT-PCR) technologies to analyse the expression of candidate genes involved in the cellular stress response. Appropriate application of qRT-PCR, however, requires the use of reference genes whose level of expression is not affected by the test, by general physiological conditions or by inter-individual variability.
  
  
  RESULTS
  The expression of nine potential reference genes was evaluated in lymphocytes of ten endurance horses during strenuous exercise. These genes were tested by qRT-PCR and ranked according to the stability of their expression using three different methods (implemented in geNorm, NormFinder and BestKeeper). Succinate dehydrogenase complex subunit A (SDHA) and hypoxanthine phosphoribosyltransferase (HPRT) always ranked as the two most stably expressed genes. On the other hand, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), transferrin receptor (TFRC) and ribosomal protein L32 (RPL32) were constantly classified as the less reliable controls.
  
  
  CONCLUSIONS
  This study underlines the importance of a careful selection of reference genes for qRT-PCR studies of exercise induced stress in horses. Our results, based on different algorithms and analytical procedures, clearly indicate SDHA and HPRT as the most stable reference genes of our pool.
authors.affiliation: Department of Pathology, Diagnostic and Veterinary Clinic, University of Perugia, Via San Costanzo 4, 06126 Perugia, Italy. katia.cappelli@unipg.it
authors.forename: Katia
authors.initials: K
authors.lastname: Cappelli
authors.forename: Michela
authors.initials: M
authors.lastname: Felicetti
authors.forename: Stefano
authors.initials: S
authors.lastname: Capomaccio
authors.forename: Giacomo
authors.initials: G
authors.lastname: Spinsanti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Silvestrelli
authors.forename: Andrea Verini
authors.initials: AV
authors.lastname: Supplizi
mesh_terms: D000465:Algorithms; D000818:Animals; D042963:Electron Transport Complex II / Q000235:genetics; D015870:Gene Expression; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D008214:Lymphocytes / Q000378:metabolism; D010805:Physical Conditioning, Animal; D016133:Polymerase Chain Reaction / Q000379:methods*; D012015:Reference Standards; D013312:Stress, Physiological
chemical_list: D042963:Electron Transport Complex II; D007041:Hypoxanthine Phosphoribosyltransferase