[Effect of 1 alpha, 25(OH)2D3 on experimental rat nephrotoxic serum nephritis].

We studied immunoregulatory effects of 1 alpha, 25(OH)2D3 in vivo using experimental rat nephrotoxic serum nephritis (NTSN). Experimental rats were divided into 3 groups according to the doses of 1 alpha (OH)D3, i.e. the control group (untreated group), the D30.02 group (0.02 microgram/Kg/day), and D30.5 group (0.5 microgram/Kg/day). The present study demonstrated that rats with NTSN receiving 0.5 microgram/Kg/day of 1 alpha (OH)D3 showed much lower urinary protein excretion as well as lesser histopathological changes in both heterologous and autologous phase as compared with rats without such treatments. On the other hand, the results in the D30.02 group varied. And also, the following were demonstrated in the D30.5 group as compared with the control group: 1) CH50 levels were maintained almost normally, 2) the staining of rat C3 was clearly lesser, 3) the number of intraglomerular OX41 and W3/13 labelled cells was significantly lower, 4) the response of cultured spleen lymphocytes stimulated with ConA and LPS was clearly inhibited, 5) the helper T cell/suppressor T cell ratio was lower, and 6) the staining of rat IgG was lesser. Therefore, it was speculated that the inhibitory effects of 1 alpha, 25(OH)2D3 on complement activation might play important roles. And also, we postulated that the following mechanisms were involved: 1) the inhibition of antibody generation due to the blocking of T lymphocyte proliferation and functions and; 2) the inhibition of intraglomerular macrophage infiltration caused by blocking of T lymphocyte functions. In conclusion, our study indicated that 1 alpha, 25(OH)2D3 had a new facet of immunoregulatory function in experimental rat NTSN.