Sprague-Dawley rats were randomly assigned to a normal group ( n = 6 ) , an IgAN model group ( n = 5 ) , a prednisone treatment IgAN group ( n = 6 ) , a 1,25-dihydroxyvitamin D3 IgAN group ( n = 6 ) , and prednisone plus 1,25-dihydroxyvitamin D3 treatment group ( n = 6 ) .