The immediate haematological response in the rat to experimental exposures of carbon monoxide.

1. A series of sixty haematocrit determinations, forty Hb evaluations, and fifty-two blood smears for reticulocyte counts were taken from splenectomized and normal female albino rats before, immediately after, and 48 hr after exposures for 10 min to two different concentrations of carbon monoxide (0.06 and 0.12%). A similar series of all three measurements was administered to lesser numbers of unexposed controls (splenectomized and normals). Both Hb and haematocrit changes show considerable individual variations in the exposed groups.2. The means for haematocrit percentage in the controls and for those exposed to 0.06% carbon monoxide show no significant differences, but the 0.12% exposure mean for both the splenectomized and normal animals show a haematocrit decrease at the immediate post-exposure examination that is significant (F = 10.7 and 6.06).3. The haemoglobin means show no significant differences in the control group. However, at the 0.12% exposure both the splenectomized and normal animals show a significant increase in the immediate post-exposure examination (F = 27.53 and 9.25).4. The means for the reticulocyte percentages in the controls show no significant differences. However, the 48 and 72 hr post-exposure examinations show means in exposed rats that are 46 and 38% greater than immediate post-exposure means and the differences are significant. In both exposed and control groups there was no significant difference between splenectomized and normal rats in respect to reticulocyte production.5. The correlation of pre-exposure and post-exposure differences for haematocrit reduction and Hb increase was extremely insignificant for controls and for those at the 0.06% exposure. It was most positive, though statistically insignificant, at the 0.12% exposure where r = 0.476 (P = 0.16) for the splenectomized and 0.210 (P = 0.55) for those with spleens.6. In the rat the spleen appears to play some role in the haematological response to carbon monoxide hypoxia since splenectomized specimens as a group significantly had a greater but less variable decrease in haematocrit, and a greater increase in Hb than specimens with spleens.