Scaling of number, size, and metabolic rate of cells with body size in mammals

The size and metabolic rate of cells affect processes from the molecular to the organismal level. We present a quantitative, theoretical framework for studying relationships among cell volume, cellular metabolic rate, body size, and whole-organism metabolic rate that helps reveal the feedback betwee...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2007-03, Vol.104 (11), p.4718-4723
Main Authors: Savage, Van M, Allen, Andrew P, Brown, James H, Gillooly, James F, Herman, Alexander B, Woodruff, William H, West, Geoffrey B
Format: Article
Language:English
Subjects:
Abdomen
Adipocytes
Adipocytes - cytology
Adipocytes - metabolism
Adipose Tissue - metabolism
Anatomy & physiology
Animals
Biological Sciences
Body Constitution
Body Size
Body Weight
Cell Size
Cell walls
Cells
Cellular biology
Cellular metabolism
Energy Metabolism
Epithelial cells
Fibroblasts - metabolism
Hepatocytes
Humans
Lungs
Mammals
Metabolism
Models, Statistical
Neurons
Neurons - metabolism
Size
Species Specificity
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Summary:The size and metabolic rate of cells affect processes from the molecular to the organismal level. We present a quantitative, theoretical framework for studying relationships among cell volume, cellular metabolic rate, body size, and whole-organism metabolic rate that helps reveal the feedback between these levels of organization. We use this framework to show that average cell volume and average cellular metabolic rate cannot both remain constant with changes in body size because of the well known body-size dependence of whole-organism metabolic rate. Based on empirical data compiled for 18 cell types in mammals, we find that many cell types, including erythrocytes, hepatocytes, fibroblasts, and epithelial cells, follow a strategy in which cellular metabolic rate is body size dependent and cell volume is body size invariant. We suggest that this scaling holds for all quickly dividing cells, and conversely, that slowly dividing cells are expected to follow a strategy in which cell volume is body size dependent and cellular metabolic rate is roughly invariant with body size. Data for slowly dividing neurons and adipocytes show that cell volume does indeed scale with body size. From these results, we argue that the particular strategy followed depends on the structural and functional properties of the cell type. We also discuss consequences of these two strategies for cell number and capillary densities. Our results and conceptual framework emphasize fundamental constraints that link the structure and function of cells to that of whole organisms.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0611235104