Specificity of antibodies to nitric oxide synthase isoforms in human, guinea pig, rat, and mouse tissues

Ten commercially available rabbit polyclonal anti-NOS antibodies were teste d for their immunohistological applicability in normal human, guinea pig, r at, and mouse organs. Most antibodies reacted as expected and described in the literature with various tissues of the investigated species. Several an tibodies did not react with the expected cell populations in a certain spec ies, or reacted in previously unknown patterns. In addition, different anti bodies to the same isoform rarely detected identical cell populations, even within one species. Most of these unexpected immunoreactivities were obser ved in bronchial epithelial, glomerular epithelial, and vascular smooth mus cle cells. These unexpected results usually occurred when the antibodies we re tested in other organs or species than that to which they were originall y raised. We therefore strongly recommend the use of anti-NOS antibodies on ly after careful immunohistological and biochemical analysis of their react ivity in the organ and species to be studied.