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

Orthostatic stimuli rapidly change plasma adrenomedullin in humans

Hypertension 1999; 34: 1147-51

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.

Practical considerations: Adrenomedullin concentrations quickly change during and after passive orthostasis, suggesting quick and sensitive baroreceptor driven secretion. Adrenomedullin may play an important role for cardiovasdcular regulatotry stability in concert with other hormonal mechanisms.