Peripheral benzodiazepine receptor (PBZr) binding sites in isolated mitochondrial (m-fractions) and microsomal fractions (p-fractions) from androgen sensitive R-3327 Dunning G and H tumors were studied. Binding in both m- and p-fractions of these tumors was specific, saturable, and of high affinity. A very high density of PBZr was found in m-fraction from both types of tumors. In p-fractions the receptor density was 4- and 7-fold lower than m-fractions from G and H tumors respectively. Receptor densities in both m- and p-fractions from the poorly differentiated fast growing G turner was significantly higher than in the corresponding fractions from the well differentiated slow growing H tumor. These data suggest that in the androgen sensitive prostatic tumors the density of PBZr may be influenced by the growth rate and degree of differentiation.

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