title: Exercise-induced changes in plasma composition increase erythrocyte Na+,K+-ATPase, but not Na+-K+-2Cl- cotransporter, activity to stimulate net and unidirectional K+ transport in humans.
abstract: We tested the hypothesis that exercise-induced changes in plasma composition result in peak stimulation of erythrocyte unidirectional K+ (JK,in) and net K+ (JK,net) transport within the first 120 s. In experimental series 1 (7 men; 2 women), plasma [K+] was continuously measured in vitro (37 degrees C) after the addition of red blood cells (RBCs) obtained from rested subjects (resting RBCs) into an exercise-simulated plasma (ESP; increased plasma osmolality, [K+], [H+], [lactate] and [adrenaline] (epinephrine)), and JK,net calculated. In experimental series 2 (7 men; 4 women), resting RBCs were incubated in true exercise plasma (TEP) obtained after two 30 s bouts of high intensity leg cycling exercise to determine JK,net and JK,in (via RBC 86Rb accumulation). JK,net of resting RBCs increased from 0.9 +/- 28.7 in resting plasma to 285 +/- 164 mmol (l RBCs)-1 h-1 in ESP and to 178 +/- 60 mmol (l RBCs)-1 h-1 after 10 s in TEP. Both JK,net and JK,in peaked within 10 s of incubation and decreased rapidly during the initial 120 s. The use of inhibitors for the Na+,K+-ATPase (ouabain) and the Na+-K+-2Cl- cotransporter (NKCC; bumetanide) indicated that rapid increases in JK,in and JK,net upon incubation of resting RBCs in TEP were due primarily to increased Na+,K+-ATPase activity; the NKCC appeared to be involved only when the Na+,K+-ATPase was blocked. It is concluded that RBCs rapidly increase JK,in and JK,net in response to exercise-induced changes in plasma composition.
authors.affiliation: Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada, N1G 2W1. mlinding@uoguelph.ca
authors.forename: Michael I
authors.initials: MI
authors.lastname: Lindinger
authors.forename: Simon P
authors.initials: SP
authors.lastname: Grudzien
mesh_terms: D000328:Adult; D001835:Body Weight; D002034:Bumetanide / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006400:Hematocrit; D006801:Humans; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D028021:Sodium-Potassium-Chloride Symporters / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium