SYMPATHETIC INNERVATION MODULATES THE EXPRESSION OF ANGIOTENSIN-II RECEPTORS IN EMBRYONIC RAT-HEART GRAFTED IN OCULO

Angiotensin II acts as a cardiac growth factor, and causes both inotro pic and chronotropic changes within the heart. In the present study, w e used an in oculo model system to examine the effects of sympathetic innervation on the density of cardiac angiotensin II receptors. Quanti tative autoradiography was used to determine the density of angiotensi n II receptors in embryonic rat hearts grafted into either sympathetic ally innervated or sympathetically denervated eye chambers of adult ho st rats. The density of specific binding to angiotensin II receptors w as nearly three-fold higher in sympathetically non-innervated compared to sympathetically innervated heart grafts (30.8 +/- 4.2 v 11.5 +/- 3 .2 fmol/mg protein). Specific binding to angiotensin II receptors in h eart grafts was displaced by addition of the AT(1) receptor antagonist losartan, but not by addition of the AT(2) receptor competitor PD 123 177. Thus, only AT(1) receptors were present in sympathetically innerv ated and sympathetically non-innervated embryonic rat hearts grafted i n oculo. We conclude that changes in sympathetic innervation caused ch anges in the density of cardiac angiotensin II receptors in the presen t study. Our results may have implications for growth and function not only during cardiac development, but also during cardiac disease. (C) 1995 Academic Press Limited