Flow-independent heterogeneity of brain capillary plasma perfusion after blood exchange with a Newtonian fluid.
Previous studies from our group have indicated a heterogeneity of plasma transit times in brain capillaries. The heterogeneity was decreased with increasing cerebral blood flow during hypercapnia. In the present study, the hypothesis was tested that these apparent changes in microvascular plasma perfusion heterogeneity depend on the existence of red blood cells (RBC). To this end, the blood of anesthetized and paralyzed rats was replaced by a shear rate-independent oxygen-carrying substitute, ultrapurified polymerized bovine hemoglobin (UPBHB). Cerebral blood flow ([14C]iodoantipyrine technique) or microvascular perfusion pattern (intravenous bolus injection of Evans blue and decapitation 3-4 s later) was measured. After exchange transfusion with UPBHB, cerebral blood flow still varied with arterial PCO2, whereas in contrast to the unexchanged condition, the heterogeneity of the intracapillary Evans blue concentration remained unchanged. Compared with the unexchanged normocapnic condition, the heterogeneity of intracapillary dye concentration was decreased by one-quarter. It is concluded that RBC contribute to the microvascular perfusion heterogeneity in the brain.
Vogel
J
J
Department of Physiology, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany.
Waschke
K F
KF
Kuschinsky
W
W
D000818:Animals; D000983:Antipyrine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001802:Blood Substitutes; D001921:Brain / Q000098:blood supply*; D002196:Capillaries / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002250:Carbon Radioisotopes; D002417:Cattle; D002560:Cerebrovascular Circulation; D006454:Hemoglobins; D006863:Hydrogen-Ion Concentration; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley
D001802:Blood Substitutes; D002250:Carbon Radioisotopes; D006454:Hemoglobins; D002245:Carbon Dioxide; D010100:Oxygen; D000983:Antipyrine; C008135:iodoantipyrine