Changes of plasma zinc and copper at various times of swimming until exhaustion, in the rat.

To characterise the response in the plasma concentration of Zn a total of 60 male Wistar rats (250 g) were divided into six groups of ten rats each. One group did not exercise; the five other groups swam at constant temperature (32/34 degrees C) and were respectively studied after 30, 60, 90, 120 min and at exhaustion. After anesthesia, rectal temperature (RT) was measured and arterial blood was obtained from the abdominal aorta. Acidbase balance, arterial blood gases and plasma concentration of Zn, Cu, Mg, Ca and Hb were measured. The swimming time at exhaustion was (mean +/- SD) 284 +/- 66 min. RT only changed after exhaustion. (H+) increased significantly at 30 min then did not change until exhaustion. (Hb) increased slightly at 90 and 120 min of swimming and after exhaustion. No changes of Mg and Ca except at exhaustion were observed (+7 and +50% respectively). On the other hand, Cu (30 min = +16%; 60 min = +29% exhaustion = +36%) and Zn (30 min = +26%; 60 min = +39%; 120 min = +66% and exhaustion = +76%) increased significantly through the two first hours of exercise. Haemoconcentration, acidosis and RT did not explain the progressive increase of Zn, which seems to be time-dependent and probably related to some degree of stress.