ANALYSIS OF SUBCUTANEOUS FLUID IN RATS

Subcutaneous implantation in rats is a commonly used model for biomate rial calcification studies. Although this model is frequently used, it s components have not been characterized with respect to calcification . Exudate from the subcutaneous spaces of 18 young rats was collected using diffusion chambers. These chambers consisted of polymethyl metha crylate tubes with 0.22 mu m pore filters covering each end allowing f luid, but not cells, to enter the chambers. Glutaraldehyde treated bov ine pericardial strips were implanted subcutaneously, inside the chamb ers and outside the chambers, to test the calcification inducing abili ties of the various environments. The animals were killed on postopera tive day 10, and the exudate and materials were collected. The exudate was analyzed for ionic calcium, total calcium, inorganic phosphorus, and albumin, and for cells by a differentiated cell smear. The materia ls were analyzed for calcification by radiography, histology, and atom ic absorption. Calcification was present in the materials inside the c hambers where no cells were present and in the materials that were not in chambers. The distinct features of the exudate were elevated ionic calcium, a high Ca x P product, and elevated phosphorus.