Kinetic studies of the Na+-K+-ATPase enzyme system in brain and heart of aging rats

L. B. Poole, M. S. Liu, P. W. Landfield

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19 Scopus citations


Kinetic analyses of the Na+-K+-adenosine triphosphatase (ATPase) system were performed in brain and heart preparations from young mature (4 mo old) and healthy aged (25 mo old) rats. The K+-activated p-nitrophenylphosphatase (K+-pNPPase) method was used to assess activity of the enzyme system. Ouabain inhibition of K-pNPPase activity was also examined. A significant age-related decrease in maximal velocity (V(max)) was found in cardiac K+-pNPPase activity, but no changes were seen in the K+ concentration for half-maximal velocity (K(0.5)). No age differences in V(max) or K(0.5) were seen for brain. No differences in ouabain inhibition were found in either brain or heart. In a second experiment, the major component of the age-related decline in cardiac K+-pNPPase activity was found to occur between 5 and 14 mo of age, a period during which plasma thyroxine had previously been found to decline in the same animals. Since peripheral Na+-K+-ATPase activity is partly thyroid hormone dependent, the age-dependent decrease in cardiac enzyme activity appears to be secondary to neuroendocrine changes.

Original languageEnglish
Pages (from-to)R850-R855
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number5
StatePublished - 1984

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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