Subtype switching of ANP receptors during in vitro culture of vascular cells

Vascular receptors for atrial natriuretic peptide (ANP) have been characterized immunochemically and found to be classified into two subtypes that show differential localization and expression. An antiserum, recognizing the protein core of the receptor, was raised against the purified bovine lung ANP receptor and used for the immunochemical subtyping. ANP receptors solubilized from the bovine jugular vein reacted strongly with the antiserum as well as the homologous lung receptor; however, the receptors from the aorta and carotid artery were recognized only weakly, indicating the presence of two types of ANP receptor in the vascular system. The one that reacts strongly with the antiserum and is distributed mainly in the venous side is termed type I and the other reacting weakly and predominating in the arteries, type II. The two subtypes were also distinguishable in their ligand specificities; the type I receptor showed a remarkably higher affinity for the ANP analogue atriopeptin I than the type II receptor. Surprisingly, similar immunochemical and biochemical analysis of the receptors on cultured vascular smooth muscle and endothelial cells revealed that the arterial cells originally expressing the type II receptor begin to express the type I receptor when cultured in vitro.