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Regional differences in cardiac myocyte dimensions and number in Sprague-Dawley rats from different suppliers
1Department of Anatomy, College of Medicine, University of South Florida, Tampa 33612.
Insights
Differences in rat heart weight stem from myocyte number, not size. Sprague-Dawley rats from different suppliers show significant variations in heart cell count, impacting overall heart mass.
Area of Science:
- Cardiovascular Research
- Comparative Anatomy
- Animal Models
Background:
- Previous studies noted larger hearts in Holtzman (H) Sprague-Dawley rats compared to Charles River (CR) rats.
- Investigating the cellular basis for these heart weight disparities is crucial for research reproducibility.
Purpose of the Study:
- To determine if differences in rat heart weight are due to myocyte size or number.
- To compare myocyte volume, length, and cross-sectional area between H and CR rats.
- To analyze regional variations in myocyte dimensions within rat ventricles.
Main Methods:
- Isolated myocytes were prepared using collagenase perfusion.
- Cell volume (V) measured by Coulter Channelyzer; cell length (L) measured directly.
- Cross-sectional area (CSA) calculated (V/L); cell number determined from isolated cells and tissue.
Main Results:
- Myocyte volume (V) and CSA were similar between H and CR rats.
- CR rat myocytes were shorter (L) but not significantly different in CSA.
- H rat hearts contained 19% more myocytes than CR rat hearts (P < 0.05).
- Regional differences in myocyte V and CSA were observed in both H and CR rats.
Conclusions:
- Rat heart weight differences between suppliers (H vs. CR) are primarily due to variations in myocyte number, not size.
- Significant regional myocyte size differences exist within rat ventricles.
- Researchers using Sprague-Dawley rats should consider supplier-dependent variations in myocyte number and heart weight.
Abstract:
Previous experiments conducted in this laboratory have indicated that adult Sprague-Dawley rats obtained from Holtzman Company (H) have hearts that are significantly larger than those obtained from Charles River (CR). To investigate potential differences in cell size and number, isolated myocytes were prepared by retrograde coronary perfusion with collagenase. Cell volume (V) was measured with a Coulter Channelyzer, cell length (L) was measured directly, and cross-sectional area (CSA) was calculated from V/L. Cell number was calculated using data from isolated cells and whole-sectioned tissue. Although V for left and right ventricular myocytes was similar in CR and H rats, myocytes from CR tended to be shorter in L (P less than 0.001), but larger in CSA (N.S.) than myocytes obtained from H rats. In both H and CR, left ventricular V and CSA were greater (P less than 0.01) in endomyocardium than epimyocardium and middle myocardium. Values for V and CSA of right ventricular myocytes were less (P less than 0.01) than those from left ventricles in both H and CR. Hearts from H had 19% more myocytes than those from CR (P less than 0.05). Values for cellular dimensions from CR generally showed less variability than those from H. We conclude that significant regional differences in myocyte size are present in rats from both H and CR. Hearts from H rats have significantly more myocytes than those from weight-matched CR rats. Therefore, investigators should be aware that differences in heart weight and myocyte number can be found in rats of the same strain, but obtained from different suppliers.