title: Changes in plasma and erythrocyte K+ during hypercapnia and different grades of exercise in trout.
abstract: Trout were exposed to hypercapnia, two levels of aerobic exercise, or three successive periods of supramaximal exercise to evaluate the effects on erythrocyte and plasma K+. During aerobic exercise, plasma K+ increased slightly with the intensity of work, while no change was found in the erythrocyte K+ content. In contrast, both hypercapnia and supramaximal exercise induced a net erythrocyte K+ uptake. This uptake changed to a net loss of K+ as arterial pH and hemoglobin-bound oxygen saturation returned to control values during recovery. The maximal rates of net K+ uptake found during hypercapnia and supramaximal exercise corresponded to 195 and 350 mumol.kg fish-1.h-1, respectively, and the maximal rates of net K+ loss found during recovery corresponded in both cases to approximately 130 mumol.kg fish-1.h-1. Hypercapnia had only a minor effect on plasma K+, but return to normocapnic conditions induced a 0.8 mM rise in plasma K+. Of this increase, approximately 70% could be accounted for by the simultaneous net release of erythrocyte K+. Each period of supramaximal exercise induced an elevated plasma K+ level, resulting in accumulation of plasma K+ despite slight decreases in plasma K+ in between the exercise periods. At the same time the net erythrocyte K+ uptake caused an estimated reduction in plasma K+ of 1.5 mM. It is concluded that both hypercapnia and supramaximal exercise cause profound net changes in the erythrocyte K+ content with significant effects on plasma K+.
authors.affiliation: Department of Zoophysiology, University of Aarhus, Denmark.
authors.forename: O B
authors.initials: OB
authors.lastname: Nielsen
authors.forename: G
authors.initials: G
authors.lastname: Lykkeboe
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D004912:Erythrocytes / Q000378:metabolism; D006935:Hypercapnia / Q000097:blood; D007700:Kinetics; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D010949:Plasma / Q000378:metabolism; D011188:Potassium / Q000097:blood*; D014337:Trout / Q000097:blood*
chemical_list: D011188:Potassium