Further metabolism of 1 alpha,25-dihydroxyvitamin D3 in target cells.

Calcitriol-inducible C-24 oxidation in target cells gives rise to calcitroic acid in a variety of cells. The pathway probably involves a transient C23-aldehyde intermediate. The pathway appears to play a crucial role in the duration of the 1,25-(OH)2D3 signal in target cells. New analogs can be designed to render the molecule more susceptible or more resistant to target cell catabolism. However, these changes do not guarantee survival of the drug due to alternative degradatory pathways.