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Species differences in sodium-potassium adenosine triphosphatase activity in the smooth muscle of the guinea-pig and rat vas deferens.

Fedan-JS; Westfall-DP; Fleming-WW
J Pharmacol Exp Ther 1978; 207(2):356-363
The activities of sodium potassium adenosine-triphosphatase (ATPase) in the guinea-pig and rat vas deferens were compared with regard to the inability of ouabain to modify the resting membrane potential of the rat but not the guinea-pig vas deferens. The species used were English-smooth-hair-guinea-pigs and Sprague-Dawley-rats. Magnesium activated and sodium potassium activated ATPase activities were determined by differential assays for different incubation conditions using tissue homogenates and subcellular fractions. The specific activity of rat vas deferens magnesium ATPase in the presence of ouabain was two to six times greater than guinea-pig vas deferens magnesium ATPase. Sodium plus potassium resulted in significant activation of the magnesium ATPase in the 10,000xg, 27,000xg, and 105,000xg pellets of guinea-pig tissue homogenates and the 10,000xg and 105,000xg pellets of rat tissue homogenates. Ouabain significantly inhibited the sodium potassium activated ATPase in all fractions from the guinea-pig. The sodium potassium activated enzyme of the 105,000xg pellet from rat was unaffected by ouabain. The percentage of total sodium potassium activated ATPase activity inhibited by ouabain was 56 percent for guinea-pig vas deferens and 30 percent for rat vas deferens. The results were discussed with regard to species differences in sodium potassium ATPase and related differences in the effects of ouabain or lowered extracellular potassium on resting membrane potential.
NIOSH-Author; Autonomic-nervous-system; Muscle-function; Physiological-response; Enzymatic-effects; Cellular-function; Laboratory-animals; Electrolytes; Cell-metabolism
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The Journal of Pharmacology and Experimental Therapeutics