Autoradiographic study of peripheral benzodiazepine receptors in animal brain tumor models and human gliomas

Abstract

In vitro binding of [ 3H]PK-11195 (1-(2-chlorophenyl)-N-methyl-(1-methylpropyl)-3-isoquinoline carboxamide) in rodent AA ascites and C6 glioma as well as in human gliomas was investigated. The B max (mean ± S.D.) of AA ascites tumor and C6 glioma is 1.39 ± 0.15 pmol/mg tissue and 4.50 ± 0.76 pmol/mg tissue, respectively. This B max is 9 and 30 times, respectively, higher than the one found in the rat cortex (0.15 ± 0.03 pmol/mg tissue). A B max of 1.26 ± 0.24 pmol/mg tissue and 0.64 ± 0.08 pmol/mg tissue was found in human malignant and low grade gliomas respectively. This B max value should be compared to 0.35 ± 0.04 pmol/mg tissue found in the normal human cortex. There are significant (P < 0.05) differences between B max in tumors and normal cortex. There was no significant difference in K D between the malignant and low grade gliomas. C6 glioma has a K D significantly greater than rat cortex. In some cases of human low grade gliomas, kinetic measurements suggested the presence of two affinity receptor sites. However, at this time, heterogeneity of the tissue cannot be excluded as being at least in part a source of this.