ANGIOTENSIN MEDIATED INTERACTION OF FETAL KIDNEY AND PLACENTA IN THE CONTROL OF FETAL ARTERIAL-PRESSURE AND ITS ROLE IN HYDROPS-FETALIS

Fetal cardiovascular control is effected by an interaction of the feta l somatic and placental circulations. Three primary regulatory mechani sms are involved: transplacental transfer of extracellular fluid, driv en by a difference in hydrostatic and oncotic pressures; modulation of fetal placental and somatic vascular resistances by means of blood pr essure controlled production of angiotensin; and somatic autoregulatio n of flow. A systems analysis incorporates these and other fetal cardi ovascular functions and this analysis was modelled for computer simula tion. Given physiologically plausible values for known cardiovascular parameters in the fetal sheep, the model reproduced in detail a variet y of experimental protocols with known outcomes; these included the no rmal fetus, the fetus after bilateral nephrectomy, the nephrectomized fetus infused with angiotensin, the intact fetus infused with NaCl sol utions, the fetus with lymphatic obstruction and the severely anaemic fetus. The systems analysis demonstrated that fetal cardiac failure co nstituted the strongest stimulus for the formation of fetal oedema of any tested pathological intervention. (C) 1997 W. B. Saunders Company Ltd.