ABSTRACT
The aim of the present investigation was to study the effect of acute swimming training with an anaerobic component on matrix metallopeptidase (MMP) activity and myosin heavy chain gene expression in the rat myocardium. Animals (male Wistar rats, weighing approximately 180 g) were trained for 6 h/day in 3 sessions of 2 h each for 1 to 5 consecutive days (N = 5 rats per group). Rats swam in basins 47 cm in diameter and 60 cm deep filled with water at 33 to 35°C. After the training period a significant increase (P < 0.05) was observed in the heart weight normalized to body weight by about 22 and 35 percent in the groups that trained for 96 and 120 h, respectively. Blood lactate levels were significantly increased (P < 0.05) in all groups after all training sessions, confirming an anaerobic component. However, lactate levels decreased (P < 0.05) with days of training, suggesting that the animals became adapted to this protocol. Myosin heavy chain-ß gene expression, analyzed by real time PCR and normalized with GAPDH gene expression, showed a significant two-fold increase (P < 0.01) after 5 days of training. Zymography analysis of myocardium extracts indicated a single ~60-kDa activity band that was significantly increased (P < 0.05) after 72, 96, and 120 h, indicating an increased expression of MMP-2 and suggesting precocious remodeling. Furthermore, the presence of MMP-2 was confirmed by Western blot analysis, but not the presence of MMP-1 and MMP-3. Taken together, our results indicate that in these training conditions, the rat heart undergoes early biochemical and functional changes required for the adaptation to the new physiological condition by tissue remodeling.
Subject(s)
Animals , Male , Rats , Matrix Metalloproteinases/metabolism , Myocardium/metabolism , Myosin Heavy Chains/metabolism , Swimming/physiology , Ventricular Remodeling/physiology , Blotting, Western , Body Weight , Gene Expression Regulation , Lactic Acid/blood , Matrix Metalloproteinases/genetics , Myocardium/enzymology , Myosin Heavy Chains/genetics , Organ Size , Physical Conditioning, Animal , Polymerase Chain Reaction , Rats, Wistar , RNA, Messenger/analysis , Time FactorsABSTRACT
Metaloproteases exercem papéis importantes em muitos processos fisiológicos em mamíferos tais como migraçäo celular, remodelamento tecidual e processamento de fatores de crescimento. Estas enzimas estäo envolvidas também na pato-fisiologia de um grande número de doenças humanas como hipertensäo e câncer. Muitas bactérias patogênicas dependem de proteases para infectar o hospedeiro. Diversas classes de metaloproteases foram descritas em seres humanos, bactérias, venenos de serpentes e insetos. No entanto, a presença e a caracterizaçäo de metaloproteases em plantas estäo pouco descritas na literatura. Neste trabalho, foi pesquisada a biblioteca de cDNA de etiquetas de seqüências expressas da cana-de-açúcar (SUCEST) para identificar, por homologia com seqüências depositadas em outros bancos de dados, famílias gênicas de metaloproteases expressas em diferentes condições. Foram utilizadas seqüências protéicas de Arabidopis thaliana e Glycine max e seqüências de nucleotídeos de Sorghum bicolor. Regiões conservadas correspondentes aos diferentes domínios e motivos de seqüência de metaloproteases foram identificadas nos cDNAs de cana-de-açúcar para caracterizar cada grupo de enzimas. Pelo menos quatro classes de metaloproteases foram identificadas na cana-de-açúcar, a saber, metaloproteases de matriz extracelular, zincinas, inverzincinas e metaloproteases dependentes de ATP. Cada uma destas classes foi analisada quanto a sua expressäo nas diferentes condições e tecidos utilizados na construçäo das bibliotecas de cDNA.