The Tissue Renin-Angiotensin System in the Female Reproductive Tissues

The renin-angiotensin system (RAS) is phylogenetically one of the oldest known physiological mechanisms (Henderson & Deacon 1993). It has been classically associated with vasoconstriction, the stimulation of aldosterone synthesis in adrenal cortex and the regulation of renal function (for review see Peach 1977, Peart 1978 and Robertson 1993). These effects were thought to be mediated exclusively by the systemic and blood borne RAS, which consists of several components. Renin and its enzymatically inactive proenzyme, prorenin, are known to be synthesized by juxtaglomerular cells in the kidney and are secreted into the bloodstream. In the circulation, renin cleaves the glycoprotein angiotensinogen secreted by the liver, to form the decapeptide angiotensin (Ang) I. The biologically active octapeptide Ang II is formed by cleavage of Ang I by angiotensin I converting enzyme (ACE). Ang II affects intracellular signalling messengers and processes by interaction with specific high-affinity Ang II receptors, which are located on cell surfaces in various tissues (Catt 1993). In this way Ang II regulates smooth muscle cell contraction, steroid synthesis, metabolic processes, growth and the process of differentiation in the target cells.