Na-K-ATPase activity decreases with aging in female rat brain synaptosomes.
To understand why elderly females are better able to tolerate hyponatremia, we measured brain Na-K-ATPase activity to determine whether this adaptive mechanism was affected by age. Using synaptosomes from 2-, 12-, and 19-mo-old female rats, we show in our results that Na-K-ATPase activity changes with age in female rats. Enzyme activity was significantly (P = 0.0026) reduced (17%) from 0.416 +/- 0.01 at 2 mo to 0.345 +/- 0.01 at 12 mo and reduced (P = 0.0001) (34%) to 0.274 +/- 0.02 micromol. min(-1). mg protein(-1) at 19 mo. To determine whether this decrease was due to reduced transport function of the Na-K-ATPase pump, we performed potassium transport using rubidium ((86)Rb+) as tracer. Ouabain-sensitive potassium uptake at 2 mo was 16.18 +/- 1.31 nmol/mg protein, was significantly (P = 0.0063) reduced (39%) to 9.79 +/- 1.44 nmol/mg at 12 mo, and was significantly (P = 0.0003) reduced (62%) to 6.12 +/- 1.05 nmol/mg protein at 19 mo. On the contrary, Na-K-ATPase activity remained elevated in males during aging. These data suggest that the Na-K-ATPase pump in female rat brain synaptosomes is decreased with increased age, and that this decrease is probably due in part to decreased potassium transport by the Na-K-ATPase pump.
Fraser
C L
CL
Department of Medicine, University of California San Francisco, 94143, USA.
Arieff
A I
AI
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000201:enzymology*; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007010:Hyponatremia / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013574:Synaptosomes / Q000201:enzymology
D004791:Enzyme Inhibitors; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium