Figure 5. Effect of aging on peripheral benzodiazepine receptor (PBR) ligand-binding characteristics. The affinity (Kd) and the number of binding sites (Bmax) for each sample were determined through Scatchard analysis using the LIGAND program as described in "Materials and Methods." Each value corresponds to the Scatchard analysis of Leydig cells purified from the pooled testes of 3 rats. ^* Significantly different from young value: P less than.05.