We wished to determine whether cardiac changes produced by CO are related to the development of pulmonary hypertension and whether they are specific for CO or also occur with high-altitude exposure. Newborn male Sprague-Dawley rats were exposed to 500 ppm CO for 32 days (CO) at Detroit, MI or to 11,500-ft simulated altitude at Fort Collins, CO (barometric pressure 495 Torr; 11K); ambient air controls were maintained at Detroit (657 ft, 200 m; AIR) and at Fort Collins (5,000 ft, 1,524 m; 5K). Rats were maintained at Fort Collins after 34 days of age. Hematocrit was elevated to a greater extent in the CO than in the 11K group 2 days postexposure; however, no differences existed 40, 76, or 112 days postexposure. Right ventricle (RV) and left ventricle plus septum (LV + S) mass in CO rats were increased 38.0 and 37.4%, respectively, relative to the AIR group 2 days after CO exposure; RV and LV + S in the 11K group were increased 55.7 and 9.3%, respectively, relative to the 5K group. Cardiac hypertrophy declined in the CO and 11K groups postexposure but remained significant for the RV, reaching 20.7% above the AIR group (CO) and 29.7% above the 5K group (11K) at 145 days of age. By use of an in vitro preparation, pulmonary vascular resistance (PVR) and pulmonary arterial pressure were significantly increased immediately after altitude but not after CO exposure and remained elevated in adulthood after altitude exposure. PVR was correlated with hematocrit in altitude- but not in CO-exposed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular hypertrophy induced in male Sprague-Dawley rats by inhalation of 500 ppm carbon monoxide (40% carboxyhemoglobin level) for 0-62 days was assessed by contiguous 2-mm thick axial cardiac cross-sections, using 32 accumulated averages of ungated fast-scan gradient-recalled nuclear magnetic resonance (NMR) images. Following final imaging, the rats were sacrificed and the hematocrit and heart mass were determined. The mean outside diameter of the left ventricle plus interventricular septum (LV + S) showed a strong correlation (r = 0.73, P less than 0.01) with the duration of CO exposure, while the correlation coefficients for the LV + S lumen diameter and wall thickness were marginally significant. The mean pleural space diameter also increased significantly (r = 0.64, P less than 0.05) with the duration of CO exposure. The ratio of the LV + S wall thickness and the lumen radius was 0.53 in the rats exposed to CO for 0-8 days; this value did not change with longer CO exposure. The LV + S outside and lumen diameter showed significant correlations to the hematocrit (r = 0.72, p less than 0.05 and r = 0.66, P less than 0.05, respectively), and the LV + S outside diameter correlated with the increase in the LV + S mass (r = 0.72, P less than 0.05). The results achieved with NMR imaging are consistent with past morphometric studies of CO-induced ventricular hypertrophy, where heart dimensions were determined in relaxed frozen tissue, and corroborate the eccentric nature of CO-induced ventricular hypertrophy.