title: Na+-K+-ATPase pump function in rat brain synaptosomes is different in males and females.
abstract: To understand the increased morbidity and mortality associated with acute hyponatremia in young women, we characterized the Na+-K+-adenosinetriphosphtase (ATPase) pump in rat brain synaptosomes to determine if this adaptive mechanism was different between the sexes. Veratridine-stimulated sodium (Na+) uptake was significantly greater (P less than 0.001) in females than in males (8.08 +/- 0.3 vs. 5.56 +/- 0.4 nmol/mg protein), suggesting either an increased rate of Na+ uptake and/or decreased extrusion of Na+ by the Na+-K+-ATPase pump in females. Uptake rate was determined by measuring Na+ transport at 5 s, and it was found to be twice as large in females as in males (1.01 +/- 0.2 vs. 0.46 +/- 0.1 nmol/mg protein). However, in the presence of 2.5 mM ouabain, uptake in both groups were similar, suggesting that the difference was probably due to decreased function of the Na+-K+-ATPase pump in females. Transport evaluation of the Na+-K+-ATPase pump showed ouabain-sensitive K+ uptake in males to be significantly greater (P less than 0.001) than in females (10.53 vs. 4.97 nmol/mg protein), and ouabain-sensitive Na+ uptake in inverted synaptosomes was 70% greater in males (4.00 vs. 2.37 nmol/mg protein). [3H]ouabain binding studies showed maximum binding capacity in males and females to be similar (103 +/- 12 vs. 110 +/- 15 pmol/mg protein), whereas the dissociation constant was significantly (P less than 0.005) greater in males (109 +/- 8 vs. 82 +/- 6 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Veterans Administration Medical Center, San Francisco, California.
authors.forename: C L
authors.initials: CL
authors.lastname: Fraser
authors.forename: P
authors.initials: P
authors.lastname: Sarnacki
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002458:Cell Fractionation / Q000379:methods; D005260:Female; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D014461:Ultracentrifugation / Q000379:methods; D014701:Veratridine / Q000494:pharmacology
chemical_list: D010042:Ouabain; D014701:Veratridine; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium