Distribution of cardiac output and organ blood content in anemic and polycythemic rats.

Organ blood content, tissue hematocrit, and regional distribution of cardiac output were measured in anemic and polycythemic rats. An increase in the blood content was found in the gastrocnemius muscle of anemic animals, together with a decrease in the blood content of the spleen. In polycythemic rats, increases in the blood content of the liver and of the kidney were detected. The blood content of the terminal vessels in the heart muscle yields a good estimate of the capillary density as demonstrated by a comparison with direct histological measurements. Variations in tissue hematocrit in the heart and gastrocnemius muscle were similar to those in venous blood whereas in other organs variations were greater than those in venous blood. Distribution of the cardiac output was changed in both experimental states; the greatest variation was found in the renal fraction (lower in anemic and higher in polycythemic rats). Finally, a possibility for comparing the relative blood flow in animals of different body we...