Salt-induced hypertension leads to development of left-ventricular hypertrophy in the Dahl salt-sensitive (Dahl/SS) rat. Before progression to left-ventricular failure, the heart initially undergoes a compensated hypertrophic response. We hypothesized that changes in myocardial energetics may be an early indicator of transition to failure. Dahl/SS rats and their salt-resistant consomic controls (SS-13BN) were placed on either a low- or high-salt diet to generate four cohorts: Dahl-SS rats on a low- (Dahl-LS) or high-salt diet (Dahl-HS) and SS-13BN rats on a low- (SSBN-LS) or high-salt diet (SSBN-HS). We isolated left-ventricular trabeculae and characterised their mechano-energetic performance. Our results show, at most, modest effects of salt-induced compensated hypertrophy on myocardial energetics. We found that the Dahl-HS cohort had a higher heat of activation, (estimated from the intercept of the heat versus relative afterload relationship generated from work-loop contractions) relative to the SSBN-HS cohort and a higher economy of contraction (inverse of the slope of the heat versus active stress relation) relative to the Dahl-LS cohort. The maximum extent of shortening and maximum shortening velocity of the Dahl/SS groups were higher than those of the SS-13BN groups. Despite these differences, no significant effect of salt-induced hypertension was observed for either peak work output or peak mechanical efficiency during compensated hypertrophy.
- Compensated hypertrophy
- Mechanical efficiency
- Myocardial energetics
- Dahl salt-sensitive rat
- Copyright © 2016, American Journal of Physiology - Heart and Circulatory Physiology