Variations of atrial natriuretic peptide, cortisol and endothelin during different body positions
© Current Science Ltd 1997
Published: 1 March 1997
Elevated cortisol in critically ill patients has traditionally been assumed to be an expression of prolonged stress, mediated by an increased activity of the hypothalamic-pituitary-adrenal axis. Recent studies have questioned this assumption by pointing out that septic and traumatized patients may have elevated plasma cortisol (C) while ACTH is suppressed . Since endothelin (E) and atrial natriuretic peptide (ANP) have been reported to be elevated in these groups of patients too, it was suggested they might influence plasmatic cortisol levels and ACTH in different ways: while E was supposed to increase plasma cortisol by a permissive effect on the adrenal action of ACTH, ANP was reported to mediate a central suppression of ACTH; the latter being insufficient to counterbalance the peripheral increase of cortisol mediated by E.
Since hormonal investigations in critically ill patients are influenced by the disease itself and the therapeutic methods applied, we chose to test the interactions between C, E and ANP in healthy adults during different body positions as a simple method of modifying central volume load and thereby the concentration of ANP.
Methods and statistical analysis
After approval by the institutional ethical authorities and informed written consent we investigated nine healthy, non-smoking males in a randomized fashion on different days [supine position (P1) first and sitting position afterwards (P2), sitting position only (P3)]. After a resting time of 20 to 30 min within each observation period we took blood samples for the measurement of the plasma concentrations of C, ANP and E.
Statistical analysis was performed with Wileoxon's test for paired observations and Spearman's signed rank correlation test. Significance level was set to P = 0.05.
C and ANP were significantly increased comparing the supine with the sitting position (C, P < 0.04 for P1 versus P2; P < 0.05 for P1 versus P3; ANP, P < 0.03 for P1 versus P3). E did not change significantly throughout the study.
We found a significant correlation between C and ANP in the supine position (r = 0.8, P < 0.03), which could not be demonstrated in the sitting position. We found no correlation between C and E and between ANP and E, respectively.
We found a positive correlation between ANP and C in the supine position and no correlation in the sitting position in healthy volunteers.
It has been suggested that the increase in ANP in critically ill patients would suppress ACTH, while a higher concentration of E would augment the adrenal's responsiveness to ACTH, leading to an increase of C. If this was true also for healthy subjects, one might expect a decrease of cortisol when ANP increases and E remains unchanged.
Sitting after supine
308.8 ± 77.5
232.7 ± 128.8
242.2 ± 60.8
28.16 ± 8.78
22.92 ± 10.9
17.26 ± 7.28
20.5 ± 3.9
20.4 ± 3.3
17.2 ± 3.1
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