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Cardiac cellular responses to altered nutrition in the neonatal rat
Insights
Nutritional state impacts cardiac development. Rats in smaller litters (6/litter) showed increased cardiac cell proliferation and ventricular growth compared to those in larger litters (18/litter).
Area of Science:
- Physiology
- Developmental Biology
- Cardiovascular Research
Background:
- Preweanling nutritional status is critical for organ development.
- Cardiac cell proliferation is a key determinant of heart growth during development.
Purpose of the Study:
- To investigate the effect of litter size, as a proxy for nutritional state, on cardiac cell division rates in developing rats.
- To determine if nutritional restriction during the preweanling period influences cardiac muscle cell proliferation and ventricular growth.
Main Methods:
- Rats were reared in litters of varying sizes (18, 12, and 6 pups per litter).
- Body weight, ventricular weights, and DNA content were measured at 21 days of age.
- Autoradiography using 3H-labeled thymidine was employed to assess cell proliferation rates.
Main Results:
- Rats in smaller litters (6/litter) exhibited significantly higher body and ventricular weights compared to those in larger litters (18/litter).
- Increased total DNA content in ventricles of 6/litter rats indicated enhanced cell proliferation, particularly in the left ventricle.
- Autoradiography confirmed increased proliferation of cardiac muscle cells, fibroblasts, and vascular endothelial cells in smaller litters, with a reduced labeling index in left ventricular muscle cells.
Conclusions:
- Nutritional state during the preweanling period significantly influences cardiac cell proliferation and ventricular development.
- Smaller litter sizes promote greater cardiac cell hyperplasia and hypertrophy, leading to enhanced ventricular growth.
- The findings highlight the sensitivity of cardiac development to early-life nutritional conditions.
Abstract:
Rats reared in litters of 18, 12, and 6 to determine whether preweanling nutritional state would alter rates of cardiac cell division, weighed 31.7, 39.1, 48.2 g, respectively, at 21 days of age. Weights of left ventricles also increased (93.2, 123.5, and 167.2 mg) as did those of right ventricles (29.9, 43.2, and 54.3 mg). Total DNA content rose in both ventricles in the pups reared 6 per litter vs. those reared 18 per litter (6/litter vs. 18/litter), but more so in the left ventricle (79%) than in the right (24%). Autoradiography confirmed that this increase in ventricular DNA resulted from increased proliferation of cardiac muscle cells, fibroblasts, and vascular endothelial cells. When 3H-labeled thymidine was injected on day 1, autoradiographs prepared on day 21 reflected an increased dilution of label in the 6/litter rats, consistent with enhanced proliferation. The labeling index and grains per nucleus of left ventricular muscle cells of the 6/litter rats were 29% (P less than 0.005) and 20% (P less than 0.001) less than those of the 18/litter rats. Less vigorous but definite hyperplasia occurred in the right ventricle, which appeared to respond with an increase more in cell size than in cell number.