Isoforms of Na,K-ATPase in Artemia salina: II. Tissue distribution and kinetic characterization

J Membr Biol. 1989 May;108(2):187-95. doi: 10.1007/BF01871029.

Abstract

To characterize the molecular properties conveyed by the isoforms of the alpha subunit of Na,K-ATPase, the two major transepithelial transporting organs in the brine shrimp (Artemia salina), the salt glands and intestines, were isolated in pure form. The alpha isoforms were quantified by ATP-sensitive fluorescein isothiocyanate (FITC) labeling. The salt gland enzyme exhibits only the alpha 1 isoform, whereas the intestinal enzyme exhibits both the alpha 1 and the alpha 2 isoforms. After 32 hours of development, Na,K-ATPase activity [in mumol Pi/mg protein/hr (1 mu)] in whole homogenates was 32 +/- 6 in the salt glands and 12 +/- 3 in the intestinal preparations (mean +/- SEM). The apparent half-maximal activation constants (K1/2) of the salt gland enzyme as compared to the intestinal enzyme were 3.7 +/- 0.6 mM vs. 23.5 +/- 4 mM (P less than 0.01) for Na+, 16.6 +/- 2.2 mM vs. 8.29 +/- 1.5 mM for K+ (P less than 0.01), and 0.87 +/- 0.8 mM vs. 0.79 +/- 1.1 mM for ATP (NS). The apparent Ki's for ouabain inhibition were 1.1 x 10(-4) M vs. 2 x 10(-5) M, respectively. Treatment of whole homogenates with deoxycholic acid (DOC) produced a maximal Na,K-ATPase activation of 46% in the salt gland as compared to 23% in the intestinal enzyme. Similar differences were found with sodium dodecyl sulfate (SDS). The two distinct forms of Na,K-ATPase isolated from the brine shrimp differed markedly in three kinetic parameters as well as in detergent sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Animals
  • Artemia / enzymology*
  • Fluorescein-5-isothiocyanate
  • Fluoresceins / metabolism
  • Histocytochemistry
  • Intestines / cytology
  • Intestines / enzymology
  • Isoenzymes / analysis
  • Isoenzymes / metabolism
  • Isoenzymes / pharmacokinetics*
  • Ouabain / pharmacology
  • Potassium / metabolism
  • Salt Gland / cytology
  • Salt Gland / enzymology
  • Sodium / metabolism
  • Sodium-Potassium-Exchanging ATPase / analysis
  • Sodium-Potassium-Exchanging ATPase / metabolism
  • Sodium-Potassium-Exchanging ATPase / pharmacokinetics*
  • Thiocyanates / metabolism
  • Tissue Distribution

Substances

  • Fluoresceins
  • Isoenzymes
  • Thiocyanates
  • Ouabain
  • Adenosine Triphosphate
  • Sodium
  • Sodium-Potassium-Exchanging ATPase
  • Fluorescein-5-isothiocyanate
  • Potassium