Microsomal (Na- +K+)-activated ATPase from frog skin epithelium. Cation activations and some effects of inhibitors.
A method is described for the extraction of microsomal ouabain-sensitive (a- + K+)-activated ATPase from separated frog skin epithelium. The method yields a microsomal fraction containing (Na+ K+)-stimulated activity in the range of 30- 40 nmol - mg -1 - min -1 at 26 degrees C. This portion which is also ouabain sensitive, is about half of the total activity in media containing Mg2+, Na+ and K+. These preparations also contain Mg2+-dependent or Ca2+-dependent activities which are not additive and which are not significantly affected by ouabain, Na+, K+ or Li+. The activations of the ouabain-sensitive ATPase activity by Mg2+, Na+, and K+ are similar to those described in other tissues. It is found that Li+ does not substitute for Na+ as an activator but in high concentrations does produce partial activation in the presence of Na+ with no K+. These results are pertinent to the reported observations of ouabain-sensitive Li+ flux across frog skin. It is concluded that this flux is not apparently due to a direct activating effect of Li+ on the sodium pump.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001386:Azides / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005665:Furosemide / Q000494:pharmacology; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology*; D003012:Microbial Collagenase; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology*; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D011892:Rana catesbeiana; D012867:Skin / Q000187:drug effects / Q000201:enzymology*; D012964:Sodium / Q000494:pharmacology*
D001386:Azides; D009840:Oligomycins; D010042:Ouabain; D000584:Amiloride; D005665:Furosemide; D008094:Lithium; D012964:Sodium; D003012:Microbial Collagenase; D000251:Adenosine Triphosphatases; D008274:Magnesium; D011188:Potassium; D002118:Calcium