Ferrous [Fe++] but not ferric [Fe] ions inhibit de novo formation of calcium pyrophosphate dihydrate crystals: possible relationships to chondrocalcinosis and hemochromatosis.

To determine the physical-chemical effects of [Fe++] and [Fe ] on calcium pyrophosphate dihydrate (CPPD) crystal formation de novo, we studied CPPD crystal formation in an established model aqueous solution mixture system using physiological concentrations of Na+, Mg++, Ca++, C1-. We found that [Fe++] greater than 1 microM or [Fe ] greater than or equal to 100 microM inhibits CPPD crystal formation under conditions of [Ca++] = 1.5 mM, [Pi] = 0.1 mM, and [PPi] = 0.1 mM that simulate CPPD formation in vivo. These experiments suggest that at biological concentrations, Fe++ acts to inhibit CPPD formation but that [Fe++] depletion therapy by removal of inhibition effects may facilitate CPPD crystal formation in articular tissues.