[en] To improve the current clinical protocols used after a burn injury,
injections of anabolic hormones like growth hormone (GH) or prolactin
(PRL), which are also known to be immunostimulators has been suggested
(Knox et al., 1995). Glucocorticoids, GH and PRL are considered stress
hormones because their secretion is strongly altered by exposure to
environmental stressors. Consistent with this concept, previous studies
have suggested that the circulating levels of each of these hormones is
increased by 24 h after a burn injury. However, the patterns of their
secretion during the first hours after the burn injury is less well
known. Working on male Sprague-Dawley rats, we have investigated
the levels of corticosterone (CS) and PRL in the first hours after burn
injury. Male rats were divided in three groups: 1) no treatment and no
handling before execution (this allowed us to monitor the normal
circadian cycle of the hormones); 2) rats are anesthesised using
pentobarbitol, shaved and prepared for the burn, but not burned
(sham-treated animals); 3) rats anesthesised and burned at 8AM. The
rats were thereafter sacrified at specific times (day 1: 9AM, 10AM,
12PM, 4PM, 7PM; day 2: 8AM, 9AM, 10AM, 4PM, 7PM). Plasma was collected
and the serum levels of CS and PRL were measured by ELISA and RIA,
respectively. The circadian cycle of CS showed the predicted nadir at
10AM, and peak at 4PM. CS levels were elevated 6-fold by 1h after burn
injury, reaching a maximum at 600ng/ml at 10AM. The concentration was
progressively reduced to normal levels by 6 h after the burn injury, and
followed the normal pattern thereafter. In sham-treated animals, CS
concentration was similar to the burned animals, but the maximum
elevation was only 3-4-fold, and the return to normal concentration was
faster, after only 4 hours. The normal circadian cycle of PRL peaked at
8AM (110ng/ml) at 8AM. In contrast to CS, serum PRL fell dramatically
following burn injury to less than 20ng/ml, and stayed low for 4h
folowing the burn injury. In sham-treated animals, the changes in PRL
were similar, but less dramatic than in the burned animals. In
conclusion anesthesia and burn stress have similar effects on hormone
secretion, but burn represents a stronger stressor. In the immediate
hours following burn injury the animal physiology is dominated by high
levels of secretion of an immunosuppressor (CS) and low levels of a
potential immunostimulator (PRL).
Research center :
University of Cincinnati (OH, USA), Department of Molecular and Cellular Physiology
