High-resolution phosphor imaging: validation for use with human brain tissue sections to determine the affinity and density of radioligand binding

Abstract

This study investigated the suitability of high-resolution storage phosphor imaging for the quantitative analysis of radioligand binding to human brain tissue. Hence, the binding of [ 3H]mazindol to the dopamine transporter in caudate–putamen tissue homogenates or frozen tissue sections apposed to either autoradiographic film or phosphor imaging plates was measured. Estimates of binding affinity were similar for homogenate studies and phosphor imaging plates (Kd=6.44±0.14 and 6.91±0.47 nM, respectively), but higher values were obtained with film autoradiography (Kd=11.31±0.82 nM). The density of binding was similar for both autoradiographic techniques (Bmax=371.9±30.8 fmol/mg estimated tissue equivalent, ETE (imaging plate) and 425±13.77 fmol/mg ETE (film)), although lower values were obtained from tissue homogenates (Bmax=64.27±6.74 fmol/mg wet weight). These results suggest that high resolution phosphor imaging can be used to analyse radioligand binding parameters in human brain tissue. Moreover, the reduced exposure time of phosphor imaging plates (e.g. 7 days vs 5 weeks) allows results to be obtained more rapidly than with conventional film autoradiography.