Plasma Catecholamine Response in Trained Rats Following Hemorrhage

Abstract

The purpose of this study was to evaluate the effect of physical training on hemorrhage-induced catecholamine release in rats. The training program consisted of swimming 5 days a week, from 15 min in the first week to 2.5 hours in the 14th week. The rats were divided into four groups. Two groups (one trained and the other untrained) were studied during hemorrhage. The third and fourth groups (one trained and the other untrained) were not subjected to hemorrhage. After 14 weeks, trained rats had a lower heart rate than untrained animals at rest (311.86 ± 8.9 vs. 361.33 ± 12.13 bpm, p <.002) for a similar body weight. The trained and untrained groups had the same blood pressure, hematocrit, and norepinephrine responses following hemorrhage. However, plasma epinephrine concentration was lower in the trained rats 15 and 25 min following hemorrhage. These results suggest a decrease of the hemorrhage-induced epinephrine secretion in trained rats. An alteration of the relationship of arterial baroreflexes and of their hormonal effectors is a potential mechanism for the reduced plasma epinephrine level in trained hemorrhaged rats. Key words: epinephrine, norepinephrine, hypotension, physical training