OBJECTIVE: Diverse glomerular disorders leadsing to progressive glomerulosclerosis share the common features of increased mRNA expression for extra- cellular matrix protein and growth factors. The precise role of angiotensin II in contributing to these disturbances is currently unknown. ACE inhibitors have been proved to be beneficial in protecting against glomerular injury in animal models and many of human glomerular diseases. Type IV collagen is a main component of extracellular matrix in the mesangium : its increased accumulation is a common pathologic finding in the glomerulosclerosis. There are some evidences that the beneficial effect of ACE inhibitor does not solely depend on the hemodynamic effect, but may be mediated by other effect. The purpose of this study is to evaluate the effects of high glucose, angiotensin II and angiotensin converting enzyme inhibitor on the expression of PC alpha1(lV) in mesansial cells(MCs). METHODS: Human mesangial cells were cultured with standard method. To investigate the effect of each drug and high glucose condition, MCs were cultured in the normal-glucose medium(100mg/dl) and high-glucose medium(450mg/dl), respectively. An- giotensin II and angiotensin converting enzyme inhibitor(captopril) were added to culture medium at final concentration of 10 M which is the physiologic dose in vivo. MCs were cultured in each condition for 3days, when the maximal effect of high glucose on MCs, and harvested for mesurement of the expression of PC alpha1(IV) mRNA. To quantitate the PC alpha(1V) mRNA levels in each condition, semiquantitatine RT-PCR was done with co-amplification of house keeping gene. RESULTS: PCa1(IV) mRNA expression was significantly increased in high-glucose medium(30mM) compared to normal-glucose medium(5.5mM)(2.28+/-0.34 vs 0.96+/-0.08, p<0.05). Administration of angiotensin ll(10(-6)M) in culture media induced a further increment in the PC a >(IV) mRNA expression to 4.64+/-0.28(p<0.05). Angiotensin II in the normal-glucose medium increased the PC alpha1(lV) mHNA expression as 2.69+/-0.23 control(p<0.05). Addition of angiotensin converting enzyme inhibitor(Capopril, 10(-6)M) in high- glucose culture medium significantly suppressed the PC alpha1(IV) mRNA expression as 0.690.11(p<0.05). CONCLUSION: High glucose concentration in culture medium significantly increases the mRNA expression of procollagen alphal(IV) than normal glucose concentration. Angiotensin II increases the collagen mRNA expression directly and this effect was significantly prevented by ACE inhibitor. This result suggests that hyperglycemia in diabetic millieu can directly increase collagen production, and ACE inhibitor may inhibit progressive glomerulosclerosis by decreasing collagen production as well as reducing intraglomerular pressure.