Blood effects of permanent normoxic hypercapnia in conventional rats

Rats were exposed 24 hours a day to carbon dioxide, 8 +/- 1%, during 2 and 4 weeks under normoxic conditions (21% oxygen). On the last day, blood was taken from the abdominal aorta under anesthesia. Leukocyte and erythrocyte counts, hemoglobin concentration, and mean cell volume were electronically measured. Hematocit and Wintrobe indexes were calculated. Leukocyte differential counts and peroxidase activity were determined on blood smears. After 4 weeks of hypercapnia, a slight decrease of neutrophilic granulocytes was observed. In mature polymorphs, peroxidase activity (cytochemically demonstrated) simultaneously decreased. Erythrocyte counts and mean cell volume remained unchanged. The most important hematological disturbance was an hemoglobin concentration drop. Consequently, it was concluded that an hypochromic anemia characterized the permanent normoxic hypercapnia in rats.