Comparison on plasma caesium kinetics in goats and horses with special emphasis on exercising horses.
OBJECTIVE
Like potassium (K+), caesium (Cs+) tends to concentrate intracellularly. The aim here was to determine how moderate exercise affects the uptake of Cs+ from blood plasma.


METHODS
After an intravenous Cs+ dose of 5 micromol kg(-1), plasma Cs+ concentration was followed for 100 min in goats and for 60 min in horses. The latter were divided into two groups, one resting and the other trotting on a treadmill (inclination 3 degrees, speed 5 m s(-1)).


RESULTS
The plasma Cs+ concentration follows a multiphase exponential decay curve, which initially could be approximated with a two-phase curve. The initially high rate constant (approximately 10 h(-1)) decreased to around 1 h(-1) in 40 min. Exercise more than doubled the rate of removal of Cs+ from plasma between 20 and 40 min after the start of exercise. After exercise, the rate returned to resting levels within 10 min. Plasma K+, on the contrary, declined for at least 20 min after exercise had ended.


CONCLUSIONS
Moderate exercise significantly increases the rate of removal of Cs+ from the bloodstream. After exercise, the rate returns to the resting levels within 10 min. The increased rate of Cs+ removal during exercise is likely due to increased activity of Na+, K+-ATPase in working skeletal muscles.
Kaikkonen
M
M
Department of Basic Veterinary Sciences, University of Helsinki, Helsinki, Finland. matti.kaikkonen@helsinki.fi
Hyyppä
S
S
D000136:Acid-Base Equilibrium; D000818:Animals; D002586:Cesium / Q000097:blood / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D006041:Goats / Q000378:metabolism*; D006736:Horses / Q000378:metabolism*; D007553:Isotope Labeling; D007773:Lactates / Q000097:blood; D018482:Muscle, Skeletal / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D011188:Potassium / Q000097:blood; D019275:Radiopharmaceuticals / Q000097:blood / Q000493:pharmacokinetics*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D007773:Lactates; D019275:Radiopharmaceuticals; D002586:Cesium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium