CHARACTERIZATION OF NATRIURETIC PEPTIDE BINDING-SITES IN THE HEART OFTHE EEL, ANGUILLA-ANGUILLA

A distinct distributional pattern of natriuretic peptide receptors has been demonstrated by in vitro quantitative autoradiography in the hea rt of Anguilla anguilla where saturable, stable, and specific binding sites for rat atrial natriuretic peptide in atrium, ventricle, and bul bus arteriosus have been detected. Competition experiments in the pres ence of either rat atrial natriuretic peptide or unlabeled eel peptide s, i.e., atrial natriuretic peptide, C-type natriuretic peptide, and v entricular natriuretic peptide, showed differences in the relative aff inity orders of these peptides in the various heart chambers. In the a trium and in the ventricular myocardium most receptors likely are type C, while B-type receptors are present in significant amounts in the v entricular endocardium and in the inner and outer layers of the bulbus arteriosus. Scatchard analysis of the competitive data indicates that in the atrium and in the ventricular myocardium only one class of rec eptors for rat atrial natriuretic peptide is present (K-d = 105 +/- 16 and 107 +/- 15 pM, respectively), while the ventricular endocardium a nd the inner and outer layers of the bulbus arteriosus contain two cla sses of binding sites (6 +/- 3.7 < K-d < 20 +/- 3.9 pM for site 1; 148 +/- 72 < K-d < 271 +/- 52 pM for site 2). (C) 1996 Wiley-Liss, Inc.