Journal of Applied Physiology, Vol 70, Issue 6 2697-2702, Copyright © 1991 by American Physiological Society
Exposure of neonatal rats to carbon monoxide alters cardiac adaptation to aortic constriction
M. O. Boluyt, D. G. Penney, F. J. Clubb Jr and T. P. White
Department of Kinesiology, University of Michigan, Ann Arbor 48109-2214.
We tested the hypothesis that a 32-day exposure of newborn rats to 500 ppm
carbon monoxide (CO) would alter the adaptive response of the heart to
aortic constriction in adulthood. At 110 days of age aortic constriction or
sham operations were performed, and hearts were studied 28 days later.
Aortic constriction increased left ventricular (LV) mass by 40% over the
control value of 611 +/- 27 mg; this adaptive response was not altered by
CO exposure. Aortic constriction and CO exposure increased right
ventricular (RV) mass by 10 and 11%, respectively, over the control value
of 185 +/- 10 mg. The effects of both experimental procedures on RV mass
were additive (23%). Peak LV pressure development (dP/dtmax) in vitro
increased 29% after aortic constriction in the nonexposed rats. CO exposure
blunted the increase in peak LV systolic pressure due to aortic
constriction. Maximum positive and negative dP/dtmax decreased by 19% after
aortic constriction and were unaffected by CO exposure. The percentage of
alpha-myosin heavy chain (MHC) in the ventricles was 94 +/- 2% in the
control group and was decreased to 81 +/- 3% by aortic constriction. In
contrast, the percentage of alpha-MHC was 87 +/- 2% for CO-exposed rats and
was not significantly altered after aortic constriction. In vitro coronary
flow was increased 18% in hearts of adult rats exposed to CO as neonates.
Exposure of neonatal rats to CO induced chronic adaptations in the
myocardium, some of which became evident in adulthood only when hearts were
challenged by aortic constriction.
