DIMINISHED CARDIAC RESPONSE TO CHRONIC VOLUME OVERLOAD IN OLDER ADULT RATS

Project Details

Description

The effects of long term hemodynamic overload in middle-aged or
older animals is unclear because most studies have used relatively
young animals or, when older ones were used, did not compare
different age groups with the same duration of the hemodynamic
load. There is good reason to believe that the adaptive process
of hypertrophic growth may be modified by the age of the animal.
Atrioventricular block (B) causes a volume overload state that can
be tolerated for long periods of time and induces considerable
cardiac hypertrophy that can be related to the amount which the
heart rate is slowed. To examine the effect of this type of
chronic hemodynamic overload in animals of different ages, we used
closed chest electrocautery to induce complete B in male, Sprague-
Dawley rats of 5,12, and 16 months of age for mean duration of 7
months. The results indicate aging over this adult period modified
the influence of long term B on cardiac size and the function of
isolated cardiac muscle. Chronic B: (1) caused cardiac
hypertrophy that was greater in the younger than older animals; (2)
prolonged contraction duration that was correlated with the extent
of hypertrophy regardless of age and (3) resulted in age-related
alterations in contractile function of isolated intact and
"chemically skinned" muscle, with the youngest B have more force
than control (C) and the older B having equal or less force than
C. Differences between younger and older B in both excitation-
contraction coupling and myofilament force production are required
to explain the observed results. These findings indicate an age-
related difference in the chronic myocardial adaptive response to
chronic atrioventricular B. The age-related differences in force
development in the present study cannot be attributed to the age-
related differences in hypertrophy. The ultimate explanation for
these findings will require a better understanding of how the
myocardium "restructures" itself under the influence of any given
hemodynamic stress and how aging affects this process.Description
StatusFinished
Effective start/end date6/15/974/30/09

Funding

  • National Institutes of Health: $55,496.00

ASJC

  • Medicine(all)

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