ABSTRACT
Affinity cytochemistry is that branch of cytochemistry that detects a ligand bound to a target site or cell. Sometimes the term is used to refer specifically to the detection of ligands bound to receptors. The labeling and detection systems depend on healthy populations of anterior pituitary cells that are dispersed and either grown in monolayer cultures, or left in suspension. The specificity of the labeling is tested by competing the biotinylated ligand with its non-biotinylated counterpart, or related peptides. In most pituitary cell types, the labeling is initially light and diffuse at the cell periphery. Electron microscopic studies show that it is mostly on the cell membrane. Once cytochemical labeling is established, there are number of experiments one can do to learn more about regulation of the expression of the receptor, binding to the ligand, and the types of target cells. Factors that inhibit binding to corticotrophs by biotinylated corticotropin releasing hormone include glucocorticoids and calcium or sodium channel blockers.
