Changes in α1- and β1-Adrenergic Receptors and Calcium Ion Binding Sites in the Fetal Myocardium of Spontaneously Hypertensive Rats (SHR)

Abstract

The present study examined changes in [3H]prazosin, [125I]iodocyanopindolol and [3H]nitren-dipine binding to α1 - and β1,-adrenergic receptors and Ca2+ binding sites of cardiac muscle isolated from fetal Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), using the radioligand binding assay method. The catecholamine concentration in the cardiac muscle of both groups was also determined. The Bmax values inβ1 -adrenoceptors and Ca2+ binding sites in SHR cardiac muscle were lower than those of WKY, but values for SHR α1,-adrenoceptors were higher than those of WKY. The Kd values of β1 adrenoceptors in cardiac muscles of SHRs were also lower than those of WKY. On the other hand, there were no differences between the catecholamine concentrations in fetal SHR and WKY cardiac muscles. Thus, significant differences in both α1- and β1,-adrenoceptors and Ca2+ binding sites were already present in fetal SHR hearts, thus suggesting that the changes in fetal hearts of SHRs may be caused by genetic defects in the mother rats at early age. © 1991, The Pharmaceutical Society of Japan. All rights reserved.