EFFECT OF SWIMMING TO EXHAUSTION, AT LOW-TEMPERATURES, ON SERUM ZN, CU, MG AND CA IN RATS

In order to study the response of plasma trace minerals during exercise in cold water at varying temperatures, three groups of ten male Wistar rats each were forced to swim until exhaustion in water at different constant temperatures (10, 20 and 32°C), while another 3 groups were kept at rest in water at the same temperatures and another group at rest out of the water, at room temperature (21°C). Rectal temperature (RT) was measured before and after the exercise. Samples of arterial blood were obtained under anaesthesia (pentobarbital) from the abdominal aorta after the exercise, and serum concentrations of Cu, Zn, Mg and Ca were determined by flame atomic absorption spectrophotometry (FAAS). The swimming time (ST) decreased in cold water, the values obtained at 10 and 20°C being 3.3% and 8.5%, respectively, of those observed at 32°C. The RT of the animals swimming at 32°C was 32.5 ± 1.8°C (mean ± SD) and fell to 25.0 ± 2.0 and to 19.1 ± 1.5°C in those swimming, respectively, at 20 and 10°C. The concentrations of Mg, Cu and Ca were significantly higher ( +50%, +36% and +7%, respectively) in animals subjected to exercise with respect to the control groups in water, although there were no differences among the three groups. On the contrary, Zn rose progressively with the increase of WT ( +32% at 10°C, +60% at 20°C and +76% at 32°C). The present data show that exercise in cold water causes in rats: 1) a significant decrease in the swimming time; 2) an increase in serum Ca, Cu and Mg not related to WT or RT and 3) an increase in serum Zn which appears to be related to WT and/or to RT. © 1990.