Developmental regulation of cation pumps in skeletal and cardiac muscle

The prenatal and early postnatal periods are critical stages during which long-term development can be affected. For example. retardation of growth during these periods is closely linked to the occurrence of adult degenerative diseases. Appropriate development of muscle is essential for numerous functions, including movement, posture. thermogenesis. breathing and maintenance of the circulation. Defects in normal muscle development could thus impair any of these functions in the neonate and may also have long-term consequences for the health of the individual. Central to normal muscle structure and function is the appropriate development not only of the sarcomeric proteins but also of the sarcolemma. transverse-tubules, sarcoplasmic reticulum and associated membrane-bound ATPases. long-term regulation of these ATPases is by changes in their concentration. whereas short-term regulation is mediated by alterations in enzyme activity. This review focuses on changes in total concentrations of Na+, K+- and Ca2+-ATPases during prenatal and postnatal life. in functionally diverse muscles of mammalian species born at different stages of maturity. Both these cation pumps belong to multigene families and changes in relative abundance of their specific isoforms are also considered because they may have important consequences for contractile performance during distinct stages of development. Finally. potential regulatory mechanisms which alter markedly during normal ontogeny are discussed. These include intrinsic factors such as hormones and contractile activity. extrinsic factors such as nutrition and environmental temperature. and interactions between these variables which are known to be especially important during postnatal development.