LOCALIZATION OF ANGIOTENSIN-II RECEPTOR SUBTYPES IN THE RABBIT HEART

Angiotensin II (Ang II) is an essential component of the renin-angiote nsin system and is partially responsible for the maintenance of hypert ension, Two major receptor subtypes have been defined for Ang II and h ave been detected in the heart of Various species. Most of the known f unctions of Ang IT are mediated via the AT(1) subtype, whereas the fun ction of the AT(2) receptor remains ill defined. In this study we aime d to localize both receptor subtypes in the rabbit heart using film an d light microscope autoradiography as well as radioligand binding assa ys on membranes. Total receptor densities in the atrium and nervous ti ssue were respectively four and nine times greater than in the ventric le, Conductive tissue shows a density between that of atrial and nervo us tissue. In the ventricle, approximately 20% of the Ang II receptors were AT(2). This receptor subtype was almost totally absent from nerv ous, conductive and atrial tissue, The limited resolution of the micro scope autoradiography method did not allow us to specify the exact cel l-type at this stage.