Endogenous biotin as a marker of adrenocortical cells with steroidogenic potential.

Interpretation of adrenal cortex phenotypes is greatly facilitated by simultaneous examination of multiple markers at single cell resolution. However, the availability of multiple appropriate antibodies can be rate limiting, while their cognate antigens are often subject to variable accessibility. Specific markers not subject to these constraints thus have obvious utility. Here we report that endogenous biotin, when detected in fixed, frozen tissue sections using fluorescent streptavidin, is a specific marker of apparently all cells with steroidogenic potential in the murine adrenal cortex. While streptavidin stains presteroidogenic and mature cortical cells, it does not label the adrenal capsule, medulla or vascular endothelium. Developmental profiles reveal adrenal endogenous biotin labeling from E13.5 through adulthood. Comparisons with zonal markers, hypothalamic-pituitary-adrenal (HPA) axis-remodeled tissue, transgenic Shh-nLacZ or Gli1-nLacZ animals, and Shh mutant embryos further demonstrate the utility of this approach. Fluorescent streptavidin applied using a simple one-step staining protocol thus provides a potent counterstain for use in adrenal analyses.