Female rats subjected to acute myocardial infarction (MI); LLLT treatment applied; MI size, systolic dysfunction, myocardial mRNA expression of interleukin-1 beta and interleukin-6, protein and mRNA levels of the Mas receptor, mRNA expression of kinin B1 and B2 receptors, plasma kallikrein, vascular endothelial growth factor (VEGF) expression, capillaries density, inducible nitric oxide synthase (iNOS) and endothelial NOS mRNA content, and plasma nitric oxide metabolites (NOx) concentration evaluated. This evidence concerns the gene KLK4 and acute myocardial infarction.