Introduction: Cardiac hypertrophy and reactive (including perivascular) and reparative fibrosis in L-NAME model are similar to that of hypertensive and cardiomyopathic patients.
The aim: To qualitatively evaluate the reactive (including perivascular) and reparative fibrosis, on days 21 and 35, occurring in hearts submitted to the L-NAME model, using special staining.
Material and methods: We utilized 33 normotensive Wistar rats. L-NAME was administered orally--in a concentration of 75 mg x 100 ml-1 in drinking water. Six rats were submitted during 21 days and an other 15 rats during 35 days. The arterial pressure was obtained on days 12, 20 and 34 using hydraulic plethysmography. On days 21 and 35 during the experiment the animals were anesthetized and submitted to cardiotomy. The hearts were fixed in Bouin fixative during 48 hours and processed using routine methods, emblocked in paraplast and cut in slices 4 to 7 microns thick. The special staining utilized were: Gomori's trichrome (aniline blue) or Masson trichrome, picro-sirius red-polarization, alcian blue technique (pH 0.5 and pH 2.5), periodic acid-Schiff technique (with and without amylases) and Weigert's resorcinol fuchsin solution (with and without oxon).
Results: Our results demonstrated an increase in the arterial pressure in animals submitted to the model. On day 21 of submission we observed modest to extensive infarct areas in the right and left ventricular myocardium. On day 35 the wide reparative areas were from old infarct areas. In some cases at day 35 the lesions reached the totality of the right ventricle in several histological slices. The right ventricle was much more affected than the left one. In both groups perivascular fibrosis was observed, nevertheless, on day 21 it was very reduced.
Discussion: The degree of direct influence of NO or hypertension produced by NO on hypertension and cardiac lesions during L-NAME model is discussed nowadays. Nevertheless, the fact is that NO deficit has great influence in several cases of cardiac lesions occurring in hypertension and also in cardiomyopathies.