Cardiac Na+, K+, Mg+2 and Ca+2 Concentrations in Chronically Exercised Rats
Bradycardia as a result of chronic exercise was induced in a group of male Sprague-Dawley rats. These experimental animals ran two hours daily, 6 days a week for 6 weeks, at a speed of 12.9 meters per minute, in a motorized running cage. Previous studies have indicated that this regimen adequately resulted in exercise bradycardia without corresponding hypertrophy. Hearts from this experimental group of chronically exercised rats were assayed via atomic absorption spectrophotometry for total tissue content of Na+, K+, Mg+2, Ca+2. These results were compared with the concentrations obtained from hearts of a group of sedentary control rats. Differences were found in the concentrations of the ions between the two groups, but these differences were all non-significant according to the Student t-test. The following concentration ratios were calculated for both groups: Na+: K+, Mg+2: Ca+2, and Ca+2 : Na+. No significant differences were found. There was considerable variation among individual results; an increased sample size might minimize the effects of this variation on the statistical tests, perhaps indicating significant differences in the ionic concentrations, particularly with regard to calcium concentration.
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