Jr. Henegar et al., ANG II-RELATED MYOCARDIAL DAMAGE - ROLE OF CARDIAC SYMPATHETIC CATECHOLAMINES AND BETA-RECEPTOR REGULATION, American journal of physiology. Heart and circulatory physiology, 44(2), 1998, pp. 534-541
The objectives of this study were I) to determine whether ANG II-induc
ed myocardial damage (ANG Dam) is mediated via the beta(1)-adrenergic
receptor, 2) to elucidate whether adrenal medulla or cardiac sympathet
ic neuron catecholamines are responsible for ANG Dam, and 3) to determ
ine whether the lack of damage after 3 days of elevated ANG II levels
is due to beta(1)-receptor downregulation. To this end, ANG II was adm
inistered to rats I) that were treated with a beta-receptor blocker 2)
after adrenal medullectomy and/or cardiac sympathetomy,: and 3) for 3
or 8 days. ANG II caused both myocyte necrosis and coronary vascular
damage after adrenal medullectomy but not after cardiac sympathectomy.
There was a 38 and 55% decrease in beta-receptor density after 3 and
8 days, respectively, of ANG II infusion, and an upregulation to contr
ol levels 5 days after a 3-day ANG II infusion was stopped. We conclud
e that cardiac sympathetic neuron catecholamines are responsible for A
NG Dam and that the acute nature of this damage is associated with a d
ownregulation of beta 1-adrenergic receptors.