THE RESPONSE OF PERITONEAL-MACROPHAGES AFTER IMPLANTATION OF SEVERAL CERAMICS AS MEASURED BY THE CHANGE OF ECTOENZYME ACTIVITY

The bioactive calcium phosphate ceramics with various calcium:phosphor us ratios: Ca/P = 1.67 (hydroxyapatite, HA), Ca/P = 1.6 and Ca/P = 1.5 (tricalcium phosphate, beta-TCP), the bioinert aluminium oxide cerami c (Al2O3) and the toxic calcium oxide ceramic (CaO) have been investig ated with respect to their ability to activate peritoneal macrophages of NMRI-mice and with respect to their influence on the extracellular nucleotide degradation of these macrophages. Two weeks after the intra peritoneal injection of a suspension of ceramic particles in an isoton e salt solution (phosphate-buffered saline = PBS), we observed that th e peritoneal macrophages were only slightly activated into the respons ive state, independent of the type of ceramic. 5'Nucleotidase (5'N) ec toenzyme hydrolyses adenosine monophosphate (AMP) and a decrease of it s activity is a general biochemical marker of activated macrophages. T his ectoenzyme activity was slightly reduced after ceramic implantatio n. The lacking rise of the extracellular diadenosine tetraphosphate (A p(4)A)-catabolism by the macrophage ectoenzyme alkaline phosphodiester ase I (APD) demonstrated that the peritoneal macrophages did not compl etely reach the responsive state. After the implantation of calcium ph osphate ceramics the extracellular adenosine triphosphate (ATP)-reduct ion was slightly diminished. After the implantation of tricalcium phos phate ceramic about 30% more peritoneal exsudate cells (PEC) were obta ined from the peritoneal cavity than after injections of pure PBS (use d as non-inflammatory control). Similar to the phenomena following the injection of thioglycollate (Tg, inflammation producing control agent ) a slightly but not significantly increased proportion of pseudopodia -building cells was observed after the implantation of the ceramic wit h Ca/P = 1.6. (C) 1998 Published by Elsevier Science Ltd. All rights r eserved.