Efeitos da restrição protéica experimental sobre a morfologia do miocárdio e as propriedades mecânicas dos miócitos cardíacos isolados em ratos Fisher após o desmame

• Autor(a) principal: Penitente, Arlete Rita
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/256
• topic: Coração; Cardiomiócito; Restrição protéica; Heart; Cardiomyocytes; Protein restriction; CNPQ::CIENCIAS BIOLOGICAS::BIOLOGIA GERAL

Nutrition deficits early in life result in adaptive changes which can permanently modify the structure of an organ or tissue. Despite the fact that cardiac function seem to be altered in rats fed low protein diet, available information about mechanics, morphology and ultrastructure of cardiomyocytes in this model is still limited. The present study investigated the relation between severe protein restriction post weaning and morphological, molecular and ultrastructural changes in ventricular cardiomyocytes in addition to the mechanics, intracellular calcium sparks and β-adrenergic system action on these cells. Animals were randomly divided in control (CG, n=36) and protein restriction (PRG, n=36) groups. After weaning (28 days), the rats were fed either control (15% casein) or low protein (6% casein) isocaloric diets for 35 days. Following this period, rats were euthanized and hearts were removed for histological, morphometric, estereological and ultrastructural analysis or processed in order to isolated cardiomyocytes by enzymatic dispersion to perform mechanic test. Results showed that protein restriction ended up in body weight, heart weight and left ventricular reduction compared to same aged control rats. These changes were accompanied by individual cardiomyocytes length, diameter and area reduction. It was also noticed 38% increase in collagen deposition in the matrix of PRG compared to CG rats. The number of cardiomyocytes was similar in both groups. Ultrastructural analyses revealed less developed myofibrils and higher proportion of less organized mitochondria and sarcoplasmic reticulum in the cells of PRG. Myocytes of PRG also showed changes in the contractile properties both in baseline and after β-adrenergic stimulation conditions. In addition, cells from PRG exhibited lower expression of SERCA2a protein and smaller calcium transient compared to CG which seems to impair the cell mechanics. Based on these findings, we conclude that severe protein restriction after weaning may modify not only morphological but also biochemical and functional aspects of the heart.