Chronic metabolic acidosis markedly induces proliferation of mesangial cells in rats / 中国病理生理杂志

ABSTRACT

AIM: To study the effects of chronic metabolic acidosis on glomerulus, mesangial cells and the production of extracellular matrix. METHODS: Chronic metabolic acidosis was induced by addition of 0.28 mol/L NH_4Cl to drinking water for 3, 7, or 14 days in male Wistar rats (n=10). Light microscope combined with computer software (Motic Images Advanced 3.2) was used to determine the effect of chronic acid loading on renal morphologic changes. The expressions of proliferation cell nuclear antigen (PCNA) and p27 in glomeruli were detected by Western blotting or immunohistochemistry. Fibronectin (FN) mRNA was detected by real-time PCR. The proliferation of mesangial cells in vitro was determined by ~3H-TdR incorporation. The concentration of FN in cultured supernatant was detected by ELISA. RESULTS: On day 1, 3, 7 and 14, the arterial pH and plasma HCO_3~- in experimental rats were significantly decreased. There was a significantly increased in the kidney weight and the ratio of kidney to body weigh in experimental rats on day 3, 7 and 14. The glomerular area and cell numbers also increased significantly. Immunoblotting demonstrated decreased p27 expression and increased PCNA expression in isolated glomeruli, and the expression of PCNA increased in a time-dependent manner following the time of chronic metabolic acidosis. Immunohistochemistry showed increased positive PCNA expression mainly localized to mesangial cells. The expression of FN mRNA was significantly elevated in experimental rats on day 7 and 14. In vitro, acid loading induced mesangial cell proliferation and synthesis of FN. CONCLUSION: These results suggest that chronic metabolic acidosis induces mesangial cell proliferation, and its mechanism may be associated with the downregulation of cell cycle kinase inhibitor p27.