title: Estrus cycle effect on muscle tyrosine kinase activity in bitches.
abstract: Estrus cycle is a well recognized cause of insulin resistance in bitches. The insulin receptor (IR) as well as the insulin-like growth factor-I receptor belong to the same subfamily of tyrosine kinase (TK) receptors. The objective of this study was to evaluate basal TK activity in muscle tissue of bitches during the estrus cycle. Twenty-four bitches were used in the study (7 in anestrus, 7 in estrus, and 10 in diestrus). Muscle samples, taken after spaying surgery to determine TK activity, were immediately frozen in liquid nitrogen and then stored at -80°C until the membranes were prepared by sequential centrifugation after being homogenized. TK activity was determined by Poly (Glu 4:Tyr 1) phosphorylation and expressed in cpm/μg of protein. TK activity was significantly lower (P < 0.001) in the animals in estrus (104.5 ± 11.9 cpm/μg of protein) and diestrus (94.5 ± 16.9 cpm/μg of protein) when compared with bitches in anestrus (183.2 ± 39.2 cpm/μg of protein). These results demonstrate, for the first time, lower basal TK activity in the muscle tissue of female dogs during estrus and diestrus, which may represent lower insulin signaling capacity, opening a new field of investigation into the molecular mechanisms of insulin resistance in dogs.
authors.affiliation: Laboratory of Metabolism and Comparative Endocrinology, Physiology Department, Basic Health Sciences Institute, Federal University of Rio Grande do Sul, Av. Sarmento Leite 500, Centro, CEP: 90050-170, Porto Alegre, Rio Grande do Sul, Brazil. gomespoppl@hotmail.com
authors.forename: Álan
authors.initials: Á
authors.lastname: Gomes Pöppl
authors.forename: Sandra
authors.initials: S
authors.lastname: Costa Valle
authors.forename: Félix
authors.initials: F
authors.lastname: Hilário Díaz González
authors.forename: Carlos Afonso
authors.initials: CA
authors.lastname: de Castro Beck
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Kucharski
authors.forename: Roselis
authors.initials: R
authors.lastname: Silveira Martins Da Silva
mesh_terms: D000818:Animals; D004285:Dogs / Q000378:metabolism*; D030762:Estrous Cycle; D005260:Female; D018482:Muscle, Skeletal / Q000201:enzymology*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*
chemical_list: D020794:Receptor Protein-Tyrosine Kinases