Reduced cardiac stiffness following exercise is associated with preserved myocardial collagen characteristics in the rat |
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Authors: | Angela J Woodiwiss Tanja Oosthuyse and Gavin R Norton |
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Institution: | (1) Laboratory of Cardiovascular Pathophysiology, Department of Physiology, University of the Witwatersrand Medical School, 7 York Road, Parktown, 2193, South Africa, ZA |
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Abstract: | We determined whether the increment in cardiac end-diastolic compliance (a reduced diastolic stiffness constant) following
endurance training is related to alterations in myocardial collagen characteristics. Sixteen weeks of habitual exercise (Ex)
in rats, which produced left ventricular (LV) hypertrophy (LVH) LV weight in g: Ex=1.01 (0.04), sedentary control = 0.89
(0.04); P<0.05], resulted in a reduced LV end-diastolic (LVED) chamber stiffness slope of the linearised LVED pressure versus LVED
internal diameter relation in kPa · mm−1: Ex=0.67 (0.03), control=0.80 (0.03); P<0.05]. The increased LVED chamber distensibility was associated with an attenuated myocardial stiffness slope of the linearised
LVED stress versus strain relation in g · cm−2; Ex=15 (3), control=25 (2); P<0.05]. Although LV total collagen content (mg) was increased in the exercised rats Ex=5.0 (0.3), control=4.1 (0.2); P<0.05], this was a reflection of the presence of LVH, as the myocardial collagen concentration (μg · mg−1 LV wet weight) was unaltered Ex=4.9 (0.2), control=4.6 (0.2)]. Furthermore, habitual exercise did not influence the percentage
of myocardial collagen extracted following cyanogen bromide digestion (an index of collagen cross-linking), i.e. Ex=38 (3),
control=38 (3)], nor the proportion of myocardial collagen phenotypes I and III I/III; Ex=3.04 (0.20), control=2.85 (0.22)].
In conclusion, exercise-induced increments in end-diastolic myocardial distensibility are unlikely to be a consequence of
alterations in the properties of myocardial collagen.
Accepted: 17 December 1997 |
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Keywords: | Exercise Diastole Collagen |
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