Localization of N-(2-diethylaminoethyl)4-iodobenzamide in the pigmented mouse eye: a microanalytical study

The 123I-N-(2-diethylaminoethyl)4-iodobenzamide (123I-BZA) is a new radiopharmaceutical used for the scintigraphic imaging of malignant melanomas. The mechanism for BZA uptake in melanic tissues is still unknown. Two methods of microanalysis, secondary ion mass spectrometry and electron probe X-ray microanalysis, were used to determine tissue distribution and subcellular location of unlabelled BZA in the C57BL6/J1 co mouse eye. Microanalysis showed elective BZA uptake by the pigmented structures of the eye: choroidal melanocytes and retinal pigment cells, where it was specifically located within melanosomes. The tropism of BZA for melanic tumours, as well as for normal pigmented tissues, could be explained by a high affinity for the melanin pigment.