Monoclonal antibodies against rat adrenocortical cell antigens.

Cell lines secreting antibodies directed against rat adrenocortical cell antigens have been produced using hybridoma techniques. As tested by immunofluorescent staining, eleven of these antibodies were specific for rat adrenocortical cells in that they did not interact with rat adrenal medulla, liver, muscle, ovary or kidney cells. Two of these antibodies were studied in greater detail. One interacted with an antigen present only in adrenal fasciculata and reticularis cells (inner zone antibody, IZA). The expression of the antigen with which this antibody interacted was increased by in vivo treatment with ACTH. The other antibody interacted with an antigen present in all three adrenocortical cell types (adrenocortical antibody ACA). Expression of this antigen was unaffected by ACTH treatment. The effect of both antibodies on steroid biosynthesis by mitochondrial and microsomal preparations of zona glomerulosa and inner zone tissue was tested. For these experiments, the antibodies were purified from culture media by Protein-A-Sepharose affinity chromatography. ACA had no effect on steroidogenesis by any preparation. IZA specifically decreased the production of 18-hydroxydeoxycorticosterone from deoxycorticosterone by the inner zone microsomal and mitochondrial fraction. The results suggest that the IZA antigen is found predominantly in the rat adrenal inner zone and that the antibody may be useful in monitoring adrenocortical zonation. In addition, the antigen would appear to have a functional role in steroid metabolism.