Related Experiment Videos
Altered sympathetic system and adrenoceptors during the development of cardiac hypertrophy
P K Ganguly1, S L Lee, R E Beamish
1Department of Anatomy, St. Boniface General Hospital Research Centre, Winnipeg, Canada.
Insights
The sympathetic nervous system and cardiac adrenoceptors are altered early in pressure overload-induced cardiac hypertrophy, affecting norepinephrine stores and receptor densities.
Area of Science:
- Cardiovascular Physiology
- Neuroendocrinology
- Molecular Cardiology
Background:
- Cardiac hypertrophy is linked to the sympathetic system and its receptors.
- Early changes in cardiac sympathetic activity and adrenoceptors during pressure overload are not well understood.
Purpose of the Study:
- To investigate alterations in the sympathetic system and cardiac adrenoceptors following aortic banding-induced pressure overload in rats.
- To understand the temporal relationship between these changes and the development of cardiac hypertrophy.
Main Methods:
- Rats underwent aortic banding for pressure overload or sham operation.
- Cardiac and plasma catecholamine levels, dopamine beta-hydroxylase (DBH) activity, and adrenoceptor densities were measured at 3, 7, and 14 days post-surgery.
Main Results:
- Aortic banding increased heart rate, systolic pressure, and cardiac RNA.
- Early decreases in cardiac norepinephrine stores and increases in plasma norepinephrine and DBH activity were observed.
- Adrenoceptor density shifted, with increased alpha-adrenoceptors early and increased beta-adrenoceptors with decreased alpha-adrenoceptors by day 14.
Conclusions:
- The sympathetic nervous system and cardiac adrenoceptors undergo significant early adaptations to pressure overload.
- These changes precede substantial increases in left ventricular mass, suggesting a role in the initial hypertrophic response.
Abstract:
Increasing experimental evidence suggests that the development of cardiac hypertrophy may involve the sympathetic system and associated receptor mechanisms. However, very little work has been done so far to understand changes in the sympathetic system and cardiac adrenoceptors soon after an increased work load is imposed on the heart. Accordingly rat hearts subjected to aortic banding-induced pressure overload were assessed 3, 7, and 14 days postoperatively. Sham-operated rats without aortic banding were used as a control group. Rats with aortic constriction had increases in heart rate, left ventricular systolic pressure, and total mechanical energy during the entire study period. The cardiac RNA level was increased without a significant increase in left ventricular mass on days 3 and 7 in aortic-banded animals; these results were associated with a decrease in the cardiac norepinephrine (NE) store and an increase in the plasma level of NE and dopamine beta-hydroxylase (DBH) activity. By day 14 a significant increase in left ventricular mass and the NE store were found; both plasma NE and DBH remained elevated. Catecholamines in other tissues such as the spleen and kidney were depleted in the banded group, whereas the dopamine level, particularly in the brain, was significantly higher during the entire study. Furthermore, the density of alpha-adrenoceptors was higher on day 3 of aortic banding, and a reciprocal correlation was evident between cardiac alpha- and beta-adrenoceptors on day 14; the density of beta-adrenoceptors was increased, whereas that of alpha-adrenoceptors was decreased in the banded group.(ABSTRACT TRUNCATED AT 250 WORDS)