ROLE OF LYSOSOMES IN CORONARY ARTERY LESIONS OF HYPERTENSIVE RATS

Electron microscopically the role of acid phosphatase (acid P) positive lysosomes in the patho?enesis of intramyocardial coronary artery lesions of hypertensive rats with bilaterally constricted renal arteries was studied. At 3 postoperative weeks, acid P positive lysosomes were increased in endothelial cells of the coronary arteries, but at 5 weeks and thereafter, they were decreased in number. In the intima, intimal smooth muscle cells with acid P positive lysosomes appeared at 3 postoperative weeks, but their number remained small as late as 9 postoperative weeks. The internal elastic lamina was fra?mented into amorphous masses from 3 postoperative weeks, at 5 weeks and thereafter the fra?mentation and disruption became severer, and at 9 weeks the lamina disappeared because of marked disruption. At 3 postoperative weeks, acid P positive extracellular lysosomes were observed in the ?aps of the fra?mented internal elastic lamina. At 5 weeks and thereafter, extracellular lysosomes and attenuated processes of medial smooth muscle cells with lysosomes were seen extending through the ?aps of the fra?mented internal elastic lamina. Necrosis of these extendin? cell processes and lysosomes remainin? after the necrosis were observed. The findin?s su??ested that the fra?mentation and lytic chan?e of the internal elastic lamina observed in hypertensive rat intramyocardial coronary arteries might be induced by extracellular lysosomes dischar?ed not only from endothelial cells and intimal smooth muscle cells but also from the extendin? processes of medial smooth muscle cells into the gaps of the internal elastic lamina. ACTA PATHOL. JPN. 36: 1529-1536, 1986.