Current topic: the uteroplacental renin-angiotensin system.

The components of the renin-angiotensin system (RAS) are expressed in the uteroplacental unit. The expression varies between species, probably due to the marked species differences in placental architecture. The conditions for angiotensin (Ang) II formation exist and Ang II receptors are present throughout the human uteroplacental unit, indicating the presence of a functional local RAS. The uteroplacental RAS interacts with other regulatory systems and in this way modulates various aspects of tissue function. It is suggested that the uteroplacental RAS is important for the regeneration of the endometrium after shedding, and for decidualization, implantation and placentation. The RAS participates in the regulation of the uteroplacental blood flow, prostaglandin synthesis and oestradiol secretion. Disturbances of the uteroplacental RAS may lead to dysfunctional bleeding and to reduced uteroplacental blood flow in pregnancies complicated by pre-eclampsia and intrauterine growth retardation.