The safety testing of medical plastics. II. An assessment of lysosomal changes as an index of toxicity in cell cultures

Abstract

Four samples of PVC containing 0, 0·17, 0·5 and 1·4% dibutyltin diacetate but otherwise identical in every respect, were used to evaluate two tissue culture methods frequently used in the safety testing of plastics. In one method (agar overlay technique), primary neonatal rat-kidney cells were grown in petri dishes, covered with 1% agar and stained with neutral red. Pieces of the plastics to be tested were then placed on the agar and the plates were examined 24 hr later. The area of neutral-red loss underneath each piece of PVC was taken as an index of toxicity. In the other method, primary neonatal rat-kidney cells were maintained in a growth medium made with serum previously used to extract dibutyltin diacetate from the plastics. In this case, lysosomal acid-phosphatase activity was used in addition to loss of neutral red to indicate cytotoxicity. With both methods, the extent of cell necrosis was in direct proportion to the concentration of dibutyltin diacetate in the plastics. The agar overlay method proved to be the more sensitive in detecting low concentrations of the cytotoxic agent in the plastics. The histochemical method demonstrated cytotoxic changes in the cells much earlier than did the loss of neutral red, but did not improve the sensitivity of the serum extract technique.