Regression of carbon monoxide-induced cardiomegaly

Publisher Website
Google Scholar
Abstract
To characterize regression of 60 day olf cardiomegalic rats, were caused to inhale CO at 2 concentrations over a 6 wk period; 400 ppm CO giving 35% HbCO (expt [experiment] 1) and 500 ppm progressively increased to 1100 ppm CO, giving a final HbCO concentration of 58% (expt 2). Rats were killed at various daily intervals upon removal from CO. Hb concentration was elevated 47% and 71% in expt 1 and expt 2, respectively, 0-3 days after cessation of CO exposure. Hematocrit was elevated and the ratio of heart weight (HW) to body weight (BW) was increased from 2.65 in controls to 3.52 in expt 1 and to 4.01 in expt 2. At 41-48 days after termination of CO inhalation there were no significant differences in Hb concentration among treated and control groups. HW/BW in expt 1 was similar to the controls, but HW/BW in expt 2 remained significantly elevated. HW, weight of the left ventricle (LV) plus interventricular septum (S), and weight of the right ventricle (RV), predicted on the basis of BW, declined to control values within 24-36 days in expt 1. In expt 2, HW and weights of LV + S and RV fell to a low point about 10% above control weights in the same time period. Myocardial lactate dehydrogenase, M subunit (M LDH), was elevated 12-14% and 5-6% above controls in LV, S, and RV in expt 1 and expt 2, respectively. These values declined sharply in the 1st 3 days when CO exposure was terminated and was followed by a more gradual decline. Control values were reached in LV, S and RV within 3 wk in expt 1. In expt 2, %M LDH did not return to control values 44 days after termination of CO exposure.