THE RATE OF BLOOD-FLOW THROUGH THE INVERTED YOLK-SAC PLACENTA OF THE ANESTHETIZED GUINEA-PIG

The rate of blood flow through the yolk sac placenta of late gestation guinea-pig fetuses was estimated by an indirect approach: radionuclide-labelled microspheres were injected in a saphenous vein and the ratio of radioactivity in the yolk sac to that in one of several reference organs was calculated. The ratio was then multiplied by a constant derived from separate experiments in which blood flows to the fetal abdominal organs and chorioallantoic placenta were determined. Stomach blood flow was positively correlated to arterial oxygen content (r=0.74, P<0.05), as was the weight-specific splenic blood flow (r=0.66, P<0.05). Perfusion of the small and large bowel, kidneys and chorioallantoic placenta was not related to arterial pH or oxygen content and these organs were used as references for the estimation of vitelline blood flow. A positive correlation was found between yolk sac blood flow and arterial oxygen content (r=0.91, P<0.01). In normoxaemic guinea-pig fetuses, yolk sac blood flow is 100–300 μl per min. © 1993, Baillière Tindall. All rights reserved.