Comparison on plasma caesium kinetics in goats and horses with special emphasis on exercising horses.

摘要

Aims: 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 mumol 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.