gamma-Interferon stimulates production of 1,25-dihydroxyvitamin D3 by normal human macrophages

We show for the first time that normal human pulmonary alveolar macrophages (PAM) markedly enhance their basal rate of the production of [3H]-1,25(OH)2D3 when cultured in the presence of recombinant gamma-interferon (gamma-IFN). The rate of conversion of [3H]-25(OH)D3 to [3H]-1,25(OH)2D3 was dose-dependent in a linear fashion. A maximal production of 1,25(OH)2D3 by PAM occurred after exposure of PAM to gamma-IFN for one day. This maximum plateau-level was sustained for at least five days. The authenticity of the putative 1,25(OH)2D3 obtained from PAM was tested by demonstrating the exact comigration of [3H]-1,25(OH)2D3 with chemically synthesized 1,25(OH)2D3 in four different HPLC-systems.