The evaluation of the responses to posture changes observed in some humoral systems, as for the Renin-Angiotensin-Aldosterone System (RAAS), is of particular relevance in the study of the regulatory mechanisms of circulation. Concerning RAAS it has been shown that this system is inhibited in supine posture and stimulated in upright posture, while still uncertainties hold for cortisol responses to posture changes. Microgravity simulations employing the head-down model at -6° (HDT -6°) have shown an even greater RAAS inhibition in respect to the supine posture, thus indicating an involvement of the side systems in the cardiovascular deconditioning. Aim of the study has been to evaluate RAAS and cortisol responses to 4hours HDT -6°. Methods: 11 fasting healthy male subjects underwent 4hours HDT-6. Blood samples were obtained before HDT and after 2 and 4 hours HDT -6°. Arterial blood pressure and heart rate were recorded beat by beat according to the same protocol. Conclusions: In accordance with current literature our results show a reduction in blood renin and aldosterone without any correlation with hemodynamic parameters. No statistically significant decrement in blood cortisol has been detected. Cortisol involvement in this experimental model will need further investigations.
|Title of host publication||European Space Agency, (Special Publication) ESA SP|
|Number of pages||3|
|Publication status||Published - 1996|
ASJC Scopus subject areas
- Aerospace Engineering