Postnatal carbon monoxide exposure: immediate and lasting effects in the rat

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Abstract
Groups of newborn rats inhaled 500 ppm CO for 32 days, after which they continued development in ambient air. The ratio of heart weight to body weight increased sharply after birth, peaked at 14 days of age and then fell progressively but remained above the of normal rats at 68 and 107 days of age. At 14 days of age, the weight of the left ventricle plus interventricular septum (LV + S) exceeded the contols by 80%; the weight of the right ventricle (RV) was 100% greater. RV weight remained significantly greater than that of the controls at 68, 107 and 217 days of age. The ratio of RV weight to LV + S weight remained higher than that of the controls during and after CO exposure. Myocardial DNA concentration (.mu.g/mg dry wt) declined more rapidly in the CO-exposed groups during the 1st 2 wk. DNA content (.mu.g/LV + S + RV) was not significantly different. There were no differenes in DNA concentration or content after CO exposure. Hyp, used as an index of collagen content, was unaffected by postnatal cardiomegaly. Hyp concentration was depressed only during the 1st 3 wk. Cardiac cytochrome c concentration was depressed and lactate dehydrogenase M subunit composition elevated only during CO exposure. Lactate dehydrogenase specific activity or myoglobin concentration was not altered during or after CO treatment. DNA or Hyp data did not provide an explanation for persistent cardiomegaly.