Rössler A, László Z, Haditsch B, Hinghofer-Szalkay HG

Orthostatic stimuli rapidly change plasma adrenomedullin in humans

Hypertension 1999; 34: 1147-51

• Physiologisches Institut, Medizinische Fakultät, Karl-Franzens-Universität Graz, Austria
• 3rd Department of Medicine, Semmelweis University Medical School, Budapest, Hungary
• Institute for Adaptive and Spaceflight Physiology, Graz

Aim of this study was to evaluate the effect of orthostasis on the time course of plasma adrenomedullin concentration (ADM).

Study design: On five different days, normotensive subjects underwent, in random order, 12º, 30º, 53º or 70º of 30 minutes passive head-up tilt (HUT), or remained in supine position, respectively. Venous blood was collected with pre-HUT supine, 3 and 27 mins of treatment (HUT12, HUT30, HUT53, HUT70) or supine, plus 2 and 50 min after treatment (supine).

Results: ADM increased significantly with HUT30, 53, and 70 in a stimulus-dependent manner. About half the increase seen with 27 minutes occurred during the first 2 minutes of upright positioning, the maximum effect with HUT70 was +70%. Elevations in norepinephrine, epinephrine, aldosterone, plasma renin activity, vasopressin, heart rate, and mean arterial pressure were also significant. Hematocrit, blood density, plasma density, and plasma volume loss rose (p<0.05) with HUT53 and 70.

In conclusion, plasma ADM rapidly increases with orthostatic challenge in a stimulus-dependent manner and also swiftly returns to baseline levels after resuming supine position.