Subcutaneously implanted tissue chambers: a pathophysiological study.

Tissue and fluid changes occurring within tissue chambers were characterised as a function of time after subcutaneous implantation in cattle. Cytological and chemical investigation revealed that the composition of fluid within chambers approached the theoretical composition of true interstitial fluid as time after implantation progressed. Erythrocyte and leucocyte numbers decreased sharply immediately after implantation and had reached stable numbers by 40 days after implantation. At this stage, chamber fluid samples had lower total protein and albumin concentrations, higher K+ and Cl- concentrations and lower pH than corresponding blood samples. Despite an ongoing low-grade chronic inflammatory reaction resulting in fibrous encapsulation of chambers, the vascularity of chamber tissue did not diminish with time after implantation. By 40 days after implantation, the cellular and chemical constituents had stabilised enough to allow use of the model to study drug distribution.