Objective: To study the effect of Enalapril on structural changes in the extracellular matrix of the media of the thoracic and abdominal segments of rat aorta under conditions that model different variants of chronic stress. Materials and methods: Wistar rats were used in experiments. Chronic adrenergic or cholinergic stresses were modeled by intraperitoneal administrations of adrenaline or Proserpine, respectively, during two weeks. The effects of Enalapril on modeled stresses were assessed by determination of the volume density of the extracellular space and collagen and elastin fibers of the media of the thoracic and abdominal segments of aorta. Results: The effects of Enalapril on extracellular matrix remodeling were most expressed in the thoracic aorta where the drug, upon the chronic adrenergic stress, prevented fibrosis and decreased collagen degradation and, upon the chronic cholinergic stress, decreased extracellular space remodeling and inhibited progression of fibrosis, in spite of a decrease in the density of elastin. In the abdominal aorta, elastin degradation increased under the effects of either, Enalapril and both variants of chronic stress. Upon chronic cholinergic stress, progressing changes in elastin network were associated with progressing fibrosis. Conclusion: Enalapryl is protective against extracellular matrix remodeling differently, depending on the conditions of stress and on the segment of aorta. Enalapryl effects were most pronounced in the thoracic segment of Wistar rat aorta upon chronic adrenergic stress and less pronounced upon chronic cholinergic stress. No protective effects of Enalapril were found in the abdominal segment of aorta upon any of stress variants.

thoracic aorta, abdominal aorta, extracellular space, collagen, elastin, remodeling, chronic stress, adrenergic stress, cholinergic stress, ACE inhibitors, Enalapril .