Aging: stimulation rate on cardiac intracellular Na+ activity and developed tension.
Previous reports suggested that Na,K-ATPase activity and Na(+)-pump capacity decrease with senescence in left atrial myocardium of F344 rats. Current experiments were designed to determine if this reduction in the Na(+)-pump affects free intracellular Na+ levels. Mean intracellular Na+ ion activity (aiNa) was measured with Na-selective microelectrodes in left atrial muscle isolated from hearts of 4-, 14- and 25-month-old F344 rats. Preparations were stimulated randomly at frequencies between 0 and 12 h. There were no age-associated differences in aiNa measured at any frequency or in the decay of Na+ activity following discontinuation of electrical stimulation. These data indicate that the aging-related decline in Na,K-ATPase does not result in elevated aiNa even at extremely high stimulation frequencies, thus suggesting that other routes of Na+ influx and efflux are also altered in atrial muscle.
Ruch
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Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205.
Im
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WB
Kennedy
R H
RH
Seifen
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E
Akera
T
T
D000375:Aging / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism / Q000502:physiology
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase