Hematologic changes in the rat during and after exposure to carbon monoxide

Rats were continuously exposed to 500 p.p.m. CO for 42 days. Hemoglobin concentration, hematocrit ratio, and erythrocyte count increased rapidly, with initial increases appearing after 4-7 days. Values of these parameters reached a plateau after 25-30 days of exposure 50 percent, 44 percent, and 42 percent above controls, respectively. Reticulocyte count peaked 600 percent above controls 7-10 days after initial exposure. This was reflected in the blood indices, mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV). MCHC fell 6 percent by the fifth day of exposure, while MCH and MCV increased 11 percent and 16 percent respectively, by the seventh day. MCHC returned to control by the thirteenth day, while MCH and MCV remained elevated until the twenty-fifth day of CO exposure. During "stable" polycythemia both MCHC and MCH were depressed, while MCV was slightly elevated above the controls. Platelet count declined substantially within 20-25 days of exposure. Hb, Hct ratio and RBC count fell to control values in the time interval between 10 and 30 days post exposure. This was accompanied by transient fall in reticulocyte count from 2.5 percent (control value) to 0.1-0,2 percent between the twelfth and twenty-sixth day after exposure. Platelet count returned to the control value when polycythemia had subsided.