NONDEFORMABLE RED-BLOOD-CELLS DO NOT INTERFERE WITH UTEROPLACENTAL BLOOD-FLOW IN THE AWAKE, LATE-PREGNANT GUINEA-PIG

The fractional entrapment of rigidified [relative to control (labeled)] red cells after the intravascular bolus injection of a cocktail of these cells, and the concomitantly induced changes in cardiac output and its distribution (microspheres) were studied in 14 awake, late-pregnant guinea pigs. In a preceding validation study in eight nonpregnant guinea pigs, it was demonstrated that with this technique reproducible data could be generated on the fractional entrapment of rigidified red cells in all organs in this species except for lungs, liver, and spleen. In response to a bolus injection with rigidified and control red cells, only the brain showed preferential entrapment of rigidified red cells, together with a small but consistent increase in blood flow. In other organs (lungs, liver, and spleen excluded), neither preferential entrapment of rigidified red blood cells nor a consistent change in blood flow could be demonstrated. The results of our study suggest that circulating nondeformable red cells have no measurable adverse effect on the perfusion of the nondiseased hemochorial placenta in the awake, late-pregnant guinea pig. This does not exclude the possibility that rigidified red cells may increase the resistance to flow in a microcirculation that has been pathologically changed by some underlying disease.