The blood supply to the abdominal organs of the fetal guinea-pig.

Guinea-pigs near term of pregnancy were anaesthetized with diazepam and sodium pentobarbitone. A fetus was exposed and the vitelline artery catheterized to measure blood pressure and heart rate or to render a reference sample of blood for the determination of organ blood flow by the microsphere technique. The radioactive microspheres were injected through a catheter in the right atrium. Mean arterial blood pressure was 4.0 kPa and heart rate was 261 beats min-1. The liver, spleen, pancreas and gut receive most of their blood supply from the same trunk as the vitelline artery. The sample from this vessel was also used to calculate blood flow to the adrenal glands, kidneys, urogenital tract, and placenta, assuming even mixing of microspheres and blood in the abdominal aorta. Umbilical blood flow, corrected to a fetal weight of 100 g, averaged 7.5 ml min-1. The adrenal glands, which are known to increase their cortisol secretion near term, had a very high rate of perfusion. If the microspheres were injected in the umbilical vein, almost all were trapped in the liver, confirming the absence of a ductus venosus in the guinea-pig fetus. Most of these microspheres were found in the quadrate lobe of the liver. Hepatic arterial blood flow was also unequally distributed, with more than two-thirds going to the right lobe of the liver. Although the distribution of portal venous blood flow is not known, it is evident that different areas of the liver are presented with blood of greatly varying oxygen saturation.