Further characterization of the glucocorticoid-induced antiphospholipase protein "renocortin"

The steroid-induced anti-phospholipase protein "Renocortin" has been further characterized by column chromatography and a monoclonal antibody. In medium devoid of foetal calf serum, renomedullary insterstitial cells in culture exposed to the anti-inflammatory steroid dexamethasone released 3 peptides of apparent MW: 15k, 30k, and 45k possessing similar biological properties to "renocortin", "lipomodulin" and "macrocortin". A monoclonal antibody directed against macrocortin also bound the 45k peptide released from the renomedullary cells. The 15k species was, like macrocortin, inactive in an "in vitro" enzymatic assay but recovered its full inhibitory activity after dephosphorylation by alkaline phosphatase treatment. We conclude that "macrocortin", "lipomodulin" and "renocortin" are similar if not identical proteins. We propose a scheme to account for "in vivo" secretion and regulation of these proteins.