HETEROGENEOUS DISTRIBUTION OF RADIOLABELED MONOCLONAL-ANTIBODY - AUTORADIOGRAPHIC EVALUATION IN THE NUDE RAT MODEL

Iodinated monoclonal antibody 96.5 was injected intravenously in the n ude rat model transplanted with human melanoma. The activity distribut ion was evaluated by: 1) direct application of dissected tissue on aut oradiographic film 2) autoradiography of whole-body sections, and 3) b eta-camera imaging of fresh frozen tissue. Method (1) is non-quantitiv e and has a pool resolution. It can only be recommended for simple scr eening. The whole-body method (2), although complicated, gives more ac curate digital information of tissue uptake in individual pixels, or i n larger regions of interest (ROIs). The beta camera technique (3) is a rapid method but its accuracy is less than the whole-body method All three methods showed that the activity distribution in the tumours wa s more heterogenous than in other tissues. An overlap of activity upta ke in tumours and other tissues was often seen. Mean uptake ratios in the whole body autoradiograms correlated well with in vivo uptake rati os from measurements in dissected tissues At present, whole body autor adiography appears to be the method of choice for imaging the uptake o f radiolabelled monoclonal antibodies in experimental animals.