ARE MAST-CELLS INVOLVED IN HYPERTENSIVE HEART-DISEASE

Objective: To evaluate the potential relationship of mast cells with m yocardial fibrosis in the cardiac ventricles of spontaneously hyperten sive rats (SHR).Design: Experiments were performed on hearts from 36-w eek-old SHR with established left ventricular hypertrophy (n = 12) and from 36-week-old normotensive Wistar-Kyoto (WKY) rats (n = 12). Furth ermore, to evaluate whether antihypertensive treatment with the angiot ensin converting enzyme inhibitor quinapril interferes with the potent ial relationship between mast cells and fibrosis in SHR, we treated 16 -week-old SHR (n = 12) with oral quinapril (10 mg/kg body weight per d ay) for 20 weeks. Methods: Mast cells were counted in 25 high-power fi elds. Toluidine blue-stained sections and avidin staining were used to detect mast cells. The extent of myocardial fibrosis was analysed in samples stained with Masson's trichrome. The amount of collagen was ev aluated morphometrically, using an automatic image analyser, and bioch emically, using myocardial hydroxyproline concentration. Results: In t he left ventricle of untreated SHR compared with age- and sex-matched normotensive WKY rats we found more extensive interstitial and perivas cular fibrosis, an increased collagen volume fraction, an increased hy droxyproline concentration and an increased number of mast cells. Simi lar but less intense abnormalities were observed in the right ventricl es of untreated SHR compared with the left ventricles of the same rats . In the left ventricles of quinapril-treated SHR compared with those of untreated SHR we found a marked decrease in fibrosis, a lower colla gen volume fraction, a lower hydroxyproline concentration and fewer ma st cells. Treatment with quinapril was also accompanied by normalizati on in the myocardial structure of the right ventricles of SHR. A posit ive correlation was found between the density of mast cells and the co llagen volume fraction in the left ventricles of all of the rats. Conc lusions: The present findings suggest that mast cells can play a part in the development of the myocardial fibrosis that occurs in the cardi ac ventricles with hypertensive cardiac hypertrophy in addition, the p resent results suggest that the ability of quinapril to interfere with mast cells might be involved in its cardioreparative properties.