Exercise- and hypertension-induced collagen changes are related to left ventricular function in rat hearts

Area of Science:

• Cardiovascular Physiology
• Cardiac Remodeling
• Biochemistry

Background:

• Chronic hypertension negatively impacts cardiac collagen profiles.
• Exercise training generally improves cardiac function.
• Collagen types I and III, and their ratio, are crucial for cardiac diastolic function, especially in hypertrophy.

Purpose of the Study:

• To investigate differences in myocardial structure and function between chronically exercise-trained and hypertensive rat hearts.
• To test the hypothesis that collagen profiles and cardiac function differ significantly between these two conditions.

Main Methods:

• Male rats were subjected to chronic exercise (XTr) or experimental hypertension (Hyp) for 10 weeks.
• Cardiac function was assessed via heart rate, blood pressure, and left ventricular pressure changes during isoproterenol stimulation.
• Myocardial collagen content and the collagen III/I ratio were analyzed using biochemical and electron microscopy techniques.

Main Results:

• Both hypertensive and exercise-trained rats showed increased heart and left ventricular weight-to-body weight ratios.
• Hypertension elevated mean arterial pressure (MAP) and diminished diastolic function ((-dP/dt)/MAP), while exercise lowered MAP and enhanced diastolic function.
• Hypertensive hearts had higher total collagen and a reduced collagen III/I ratio compared to exercise-trained hearts, with a negative correlation between collagen III/I and diastolic function.

Conclusions:

• Adaptations in left ventricular collagen, particularly the collagen III/I ratio, are closely related to changes in diastolic function.
• Chronic hypertension leads to increased collagen accumulation and impaired diastolic function.
• Chronic exercise training promotes favorable collagen remodeling and improved diastolic function.