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Larval salt gland ofArtemia salina nauplii. Localization and characterization of the sodium+potassium-activated Adenosine Triphosphatase
Ewing, R.D.; Peterson, G.L.; Conte, F.P. (1974). Larval salt gland ofArtemia salina nauplii. Localization and characterization of the sodium+potassium-activated Adenosine Triphosphatase. J. Comp. Physiol. A Sens. Neural Behav. Physiol. 88(3): 217-234
In: Journal of Comparative Physiology A. Sensory, Neural, and Behavioral Physiology. Springer: Heidelberg; Berlin. ISSN 0340-7594; e-ISSN 1432-1351
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| Auteurs | | Top |
- Ewing, R.D.
- Peterson, G.L.
- Conte, F.P.
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| Abstract |
The naupliar stage of Artemia salina has been found to contain large amounts of an ATPase which requires the presence of Mg++, is stimulated by Na+ and K+, and is sensitive to ouabain. Upon cell fractionation, sixty percent of the Na+K-activated ATPase activity was present in a heavy membrane fraction which accompanied mitochondria, and twenty percent of the activity was found in the microsomal fraction. Separation of the heavy membranes containing the Na+K-activated ATPase from mitochondria was accomplished by sucrose density gradient centrifugation.Kinetic characterization of the Na+K-activated ATPase was examined with both mitochondrial and microsomal preparations. No significant differences were observed between the two preparations. Maximal enzyme activity occurred at pH 7.2 and a temperature of 45 ° C. Half maximal inhibition of enzymatic activity occurred with ouabain concentration of 8 × 10-6 M. Half maximal activation of the enzyme by ATP and MgCl2 occurred at 8 × 10-4 and 1 × 10-3 M, respectively, with an optimal Mg++/ATP ratio of 2.0. NaCl and KCl (or NH4Cl) were required for activity, with half maximal activation at 1 × 10-2 and 9 × 10-3 M (or 2.1 × 10-2 M), respectively. The optimal Na+/K+ ratio was 4.0, although enzymatic activity occurred through a wide range of ratios. In contrast, survival of nauplii was reduced in media in which the Na+/K+ ratio was less than 10.Anatomical localization of the enzyme in nauplii indicated that the abdominal region contained 44% of the total Na+K-activated ATPase activity, while the cephalothoracic region contained 54% of the total activity. Isolated larval salt glands contained 10% or less of the total activity. In contrast, the adult leg segments containing the salt-transporting organs showed 54% of the total Na+K-activated ATPase activity. |
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