A new low-molecular-weight calcium-binding ligand in rat small intestine.

Three calcium-binding ligands in the cytosol of rat small intestine have been separated using Sephadex G-75 column chromatography. The estimated molecular weights of these ligands were 85,000, 10,000, and 800, respectively. The two high-molecular-weight ligands were found only in young rats, while the low-molecular-weight calcium-binding ligand was found in all age groups and appeared to be a calcium-bound prostaglandin metabolite. Oral administration of arachidonic acid increased and PGE2 decreased in vivo calcium absorption, while PGF2 administration showed no discernible effect on this parameter. These results suggest that the intestinal calcium transport mechanism may be modulated by prostaglandins and related metabolites.