The effect of repetitive haemorrhage on plasma cortisol, beta-endorphin and N-terminal pro-opiomelanocortin in conscious sheep.
We measured the effect of repeated haemorrhagic stress, performed on four consecutive days in conscious adult sheep, on the plasma concentrations of cortisol and ACTH-related peptides to determine whether the pituitary-adrenal response was altered by stress repetition. Peptides from the C-terminus of the ACTH pro-hormone was measured by beta-endorphin RIA. Glycopeptides derived from the N-terminus of the ACTH pro-hormone were measured by tau 3-MSH RIA. The immunoreactive tau 3-MSH in sheep plasma was found to have an apparent molecular weight of approximately 10,000 by gel chromatography through Sephadex G-75, which is similar to the size of the major circulating form of pro-tau-MSH found in human and rat plasma. Daily haemorrhage consistently elevated plasma concentrations of cortisol and pro-tau-MSH. There was no significant difference in the daily responses of either cortisol or pro-tau-MSH when considered individually. However, there was a significant change over the four days in the relationship between the cortisol and pro-tau-MSH responses, as judged by analysis of variance of the difference in daily z-scores of cortisol and pro-tau-MSH. This trend indicated a relative increase in the secretion of pro-tau-MSH from the pituitary compared to the cortisol response, and suggested that repeated exposure to stressful stimuli may alter the pituitary-adrenal-axis.
Smith
R
R
Faculty of Medicine, University of Newcastle, New South Wales, Australia.
Lovelock
M
M
Owens
P C
PC
Chan
E C
EC
Falconer
J
J
D000818:Animals; D006470:Hemorrhage / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood*; D010446:Peptide Fragments / Q000097:blood*; D011333:Pro-Opiomelanocortin / Q000097:blood*; D012756:Sheep; D013312:Stress, Physiological / Q000378:metabolism; D013997:Time Factors; D001615:beta-Endorphin / Q000097:blood*
D010446:Peptide Fragments; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; D006854:Hydrocortisone