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Myocardial collagen in different forms of heart hypertrophy in the rat
Insights
Heart enlargement in rats, caused by hypertension or aortic stenosis, increases collagen (hydroxyproline) content. This collagen increase correlates positively with the degree of cardiac hypertrophy, except in early-stage Goldblatt rats.
Area of Science:
- Cardiovascular Research
- Biochemistry
- Physiology
Background:
- Cardiac hypertrophy, or heart enlargement, is a significant pathological condition.
- Hydroxyproline concentration is a key indicator of collagen content and cardiac fibrosis.
Purpose of the Study:
- To investigate the relationship between cardiac hypertrophy and collagen content (hydroxyproline concentration) in rat hearts.
- To analyze these changes across different models of induced heart enlargement.
Main Methods:
- Inducing cardiac hypertrophy in rats using four methods: renal hypertension, spontaneous hypertension, aortic stenosis, and swimming training.
- Measuring hydroxyproline concentration in normal and hypertrophied cardiac tissues, including separate analysis of ventricular walls and layers in spontaneously hypertensive rats.
Main Results:
- Cardiac hypertrophy induced by hypertension and aortic stenosis was associated with increased hydroxyproline concentration.
- A positive correlation was observed between the degree of hypertrophy and the increase in hydroxyproline concentration.
- In spontaneously hypertensive rats, endomyocardial areas showed a greater increase in hydroxyproline compared to epimyocardial areas.
- Swimming training induced minimal hypertrophy with no significant change in hydroxyproline concentration.
- Early-stage Goldblatt rats showed hypertrophy without a significant change in hydroxyproline.
Conclusions:
- Cardiac hypertrophy, particularly due to hypertension, leads to increased collagen deposition in the heart.
- The extent of collagen increase is linked to the severity of cardiac enlargement.
- Regional differences in collagen accumulation exist within the hypertrophied heart, notably in endomyocardial regions.
Abstract:
The hydroxyproline concentration, representing collagen content, has been investigated in normal and hypertrophied rat hearts. Enlargement of the heart was produced by four methods: a. Experimental renal hypertension (Goldblatt rats); b. Spontaneous hypertension (SHR); c. Experimental aortic stenosis; d. Swimming training. In spontaneously hypertensive rats the free wall of the right and left ventricles and the septum were analyzed separately. Furthermore, the left ventricular free wall was divided into endomyocardial and epimyocardial slices to permit separate investigation. Otherwise, the hydroxyproline concentration was always analyzed in left ventricular tissue. In swimming rats the absolute enlargement was very slight (15%), whereas the hydroxyproline concentration remained unchanged. The degree of hypertrophy was greater in all other experimental animals and was associated with an increase in hydroxyproline concentration in hypertrophied tissue. There was a positive correlation between the rate of hydroxyproline concentration increase and the degree of hypertrophy. The findings only vary in different experimental groups of Goldblatt rats at an early stage. Four weeks after surgery we found a left ventricular hypertrophy of 34%, whereas hydroxyproline concentration in left ventricular tissue was unchanged in comparison to control values. In spontaneously hypertensive rats the increase in hydroxyproline concentration in endomyocardial areas was considerably greater than in epimyocardial areas. Significant differences in water retention and nitrogen content (microgram/mg dry tissue) of hypertrophied and normal ventricular tissue were not found.