Angiotensin II enhances glomerular expression of a nonmuscle myosin heavy chain, SMemb, with extracellular matrix accumulation.

Background/Aims: We previously showed that the mesangial expression of nonmuscle-type myosin heavy chain, SMemb, was related to glomerular sclerosis. Although angiotensin 11 (All) is known to promote the glomerular accumulation of extracellular matrix and sclerosis, the effect of All on the mesangial expression of SMemb is unknown. Thus, we investigated the effect of All on the mesangial expression of SMemb and synthesis of fibronectin. Methods: We continuously administered All to Sprague-Dawley rats with subcutaneous osmotic minipumps for 14 days. Control animals received normal saline instead. The effects of oral administration of an All type 1 (AT1) receptor antagonist, candesartan cilexetil, and a vasodilator, hydralazine, were also examined. Results: Semiquantitative immunohistochemical evaluation and Western blot analysis showed that All significantly enhanced glomerular expression of SMemb (0.87 +/- 0.33 vs. 0.40 +/- 0.19 for immunohistochemical grading, p < 0.05; 2.55 +/- 0.88 vs. 1.16 +/- 0.75 for Western blot analysis, p < 0.05). Glomerular fibronectin was also increased in All-administered rats (301.7 +/- 206.8 ng/5 pg protein vs. 95.8 +/- 81.3 ng/5 pg protein, p < 0.05). Candesartan cilexetil attenuated these effects. On the other hand, hydralazine did not change the glomerular expression of SMemb enhanced by All administration. Conclusion: All induced a phenotypic alteration in mesangial cells, enhanced the mesangial expression of SMemb and stimulated the fibronectin synthesis. These results suggest that the mesangial expression of SMemb is related to glomerular matrix accumulation and that All mediates both mesangial processes via AT1 receptors. Copyright (C) 2002 S. Karger AG, Basel.