Comparison of LR White and Unicryl as embedding media for light and electron immunomicroscopy of chromaffin cells.

LR White and Unicryl are members of the same family of acrylic embedding resins and are very suitable for "on grid" postembedding immunogold labeling. We studied the ultrastructure of LR White- and Unicryl-embedded cultured chromaffin cells and the immunolocalization of three chromaffin cell proteins, the enzymes dopamine-beta-hydroxylase (DbetaH) and tyrosine hydroxylase (TH), and the membrane fusion and Ca2+ channel protein synexin (annexin VII). We report here that Unicryl is preferable to LR White as an embedding medium for electron microscopy when osmium tetroxide fixation is omitted. The basis for this distinction is better ultrastructural preservation and improved immunodetection efficiency.