Whole-body autoradiographic study of [3H]-PK 11195 distribution in dunning AT-1 tumour-bearing rats.

ABSTRACT

In vivo binding of [3H]-PK 11195 to peripheral benzodiazepine binding sites in Dunning AT-1 prostatic tumour-bearing rats was investigated by whole-body autoradiography. Distribution and retention of PK 11195 in tumour and other organs was examined at different time intervals. Autoradiograms indicated PK 11195 binding sites in the periphery of the tumour, whereas no or little binding was detected in the prostate. Among other organs, adrenal cortex was most intensely radiolabelled. Administration of nonradioactive PK 11195 before [3H]-PK 11195 blocked binding in all organs more completely than in tumour, kidney, and adrenal cortex, where low levels of radioactivity still were present. Radioactivity in the tumour, contrary to other organs, seemed to increase with time, indicating a slow uptake with large capacity. High performance liquid chromatography analysis of extracted radioactivity from the tumour showed that almost all radioactivity consisted of intact [3H]-PK 11195. These results indicate binding in vivo of PK 11195 to peripheral benzodiazepine receptors in Dunning AT-1 rat prostatic tumours and a large capacity for uptake and retention of [3H]-PK 11195 in tumours.