STUDIES ON THE REDUCTION OF AORTIC CALCIFICATION BY ALKALI CITRATES IN AN EX-VIVO TISSUE-PREPARATION IN THE RAT

The effect of orally administered alkali citrates on the calcification of arterial vessel was studied in the rat. Freshly dissected aortic s egments were placed in Millipore diffusion chambers and grafted intrap eritoneally. Within 21 days calcification of the media had developed. Under treatment with 2.1 mmol citrate per animal and day a significant decrease in histologically detectable calcification areas occurred, a s assessed by greatest thickness and longitudinal expansion. This effe ct was more pronounced with potassium citrate and potassium sodium cit rate, and less marked with sodium citrate. The calcium and phosphorus content of aortic tissue remained unchanged, but magnesium increased s ignificantly. The spheroid particles deposited in the media were chara cterized in more detail by electron microscopy and elemental microanal ysis, X-ray diffraction, and determination of the molar calcium-phosph orus ratio. The combined data suggest that in the model selected for s tudying biocalcification not mature hydroxyapatite but some precursor of this substance is deposited, and that in animals receiving alkali c itrate treatment deposition of amorphous calcium phosphate is likely. It is concluded that in the ex vivo aortic wall preparation oral alkal i citrates a) bring about a reduction in calcification areas in the me dia layer b) impair the maturation of hydroxyapatite and its depositio n in the arterial tissue; c) promote the accumulation of magnesium. Wh ether these results are of significance for the calcification of arter ies in situ and treatment regimens is unknown.