Hematologic responses to carbon monoxide and altitude: a comparative study.

Groups of 40- and 90-day-old rats were exposed to 500 ppm CO (HbCO=31-43%) and simulated altitude (15,000 ft). Resulting hematologic changes were monitored after 1 day, 1 wk, 3-4 wk, and 9-11 wk of exposure. The two treatments resulted in similar changes in hemoglobin (Hb) and hematocrit ratio (Hct) in the young rats, while in the older group there were several small, but significant differences in these parameters. Mean corpuscular hemoglobin concentration (MCHC) fell 12.4-15.1% during the 1st wk of exposure in all groups except the young altitude rats, which remained at the control value. The former groups returned to control levels by the 3rd to 4th wk of exposure. Red cell 2,3-diphosphoglycerate (2,3-DPG) increased 21.6-26.1% above control during 3-4 wk of altitude exposure, but later (9-11 wk) returned toward control levels. CO exposure resulted in a sharp decrease in 2,3-DPG after 1 day of exposure only in the young rats. 2,3-DPG level progressively decreased with age in control rats. The effects of CO and altitude although similar in several respects (i.e., Hb, Hct, MCHC) differ with regard to red cell 2,3-DPG.