A review of the renin-angiotensin system in the normal heart.

This review describes the vascular and cardiac tissue renin-angiotensin system (RAS), a so-called autocrine hormonal system as opposed to the circulating endocrine system. The existence of this autocrine system is suggested by the persistence of elevated concentrations of angiotensin II (Ang II) following binephrectomy. There is considerable evidence to support the concept of an autocrine RAS, but the functional aspects of such a system remain controversial: (a) Cultured endothelial cells from blood vessels can, for example, synthesize renin, but angiotensinogen messenger RNA (mRNA) is only present in perivascular adipocytes. (b) In the myocardium, there are obviously problems raised depending on the animal species considered: only rats apparently lack ventricular RAS, but tissue RAS is present in their atrial and conducting tissue system. In other species such as rabbit, the situation is quite different. In addition to the inotropic effect of Ang II, it has recently been demonstrated that this substance may determine the expression of the cardiac genome (oncogenes).