Static and dynamic properties of tissue cage fluid in rabbits

The properties of tissue cage fluid in a steel net tissue cage model in rabbits were compared to those of serum by determination of the protein profile, the cell contents, and the pharmacokinetics of 125I albumin, 3H sucrose and 3H fusidic acid. The dominating serum proteins demonstrated by crossed immunoelectrophoresis were also detected in tissue cage fluid but at lower levels and at various ratios. The cell pattern gradually changed from an initial dominance of polymorphonuclear cells to lymphocytes during the five weeks following the subcutaneous implantation of the cages. The distribution of the highly protein-bound fusidic acid was markedly slower and the maximal tissue cage fluid level significantly lower than that of sucrose. Equilibrium of 125I albumin between serum and tissue cage fluid was slowly achieved during the following two weeks. The advantages and disadvantages of tissue cage models for studies of drug pharmacokinetics are discussed. The properties of tissue cage fluid and the possibility of repeated sampling make the model suitable for studies of experimental local infections. The influence of therapeutic agents and the host's response to the infectious process may also be elucidated.