We developed an immunohistochemical method for visualization of vitamin D (VDR) and estrogen receptors (ER) in cryostat sections, using monoclonal antibodies (MAb) to the vitamin D receptor and estrogen receptor, respectively. This method is based on an avidin-biotin labeling technique (LAB). To establish a reliable and sensitive method which can be used easily as a routine diagnostic procedure, we systematically compared four different immunoenzymatic methods with respect to their efficiency in detecting vitamin D and estrogen receptors. Compared to the indirect bridged avidin-biotin (IBRAB), the peroxidase- anti-peroxidase (PAP), and the avidin-biotin complex (ABC) methods, the LAB method produced stronger staining intensities and had higher detection efficiency for both vitamin D and estrogen receptors. In addition, the LAB method had a higher spatial resolution compared to the ABC technique in detection of VDR in normal human skin biopsies. In the case of steroid receptors, i.e., nuclear antigens, immunohistochemistry must deal with a relatively low number of antigenic sites per cell, restricted accessibility of the antigens, and slight differences in antigen concentrations among cells. Under these particular conditions, the chemical properties of the conjugates used in the LAB method may explain why it is superior to the other methods. Consequently, the LAB method is recommended for visualization of ER and VDR.
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