the principal cause of the clinical failure of bioprosthetic heart valves fabricated from glutaraldehyde-pretreated porcine aortic valves is calcification. other prostheses composed of tissue-derived and polymeric biomaterials also are complicated by deposition of mineral. in this study the authors focused on the relationship of ap to early events in calcification, and the inhibition of both calcification and ap activity by fecl//3 and alcl//3 preincubations the results of these studies are as follows: (a) extractable ap activity is present in fresh but not glutaraldehyde-pretreated bovine pericardial tissue. (b) extrinsic ap is rapidly adsorbed following implantation, with peak activity at 72 h (424 $plus or minus$ 67.2 nm pnpp/mg protein/min enzyme activity $left bracket$ units $right bracket$ ), but markedly lesser amounts at 21 days (96.8 $plus or minus$ 3.9 units). (c) simultaneously to the ap activity maximum, bulk calcification is initiated, with gpbp calcium levels rising from 1.2 $plus or minus$ 0.1. (edited author abstract) 83 refs