Exercise-induced increase in circulating adrenomedullin is related to meanblood pressure in heart transplant recipients

Adrenomedullin (ADM) is a newly discovered potent vasorelaxing and natriure tic peptide that recently has been shown to be increased after-heart transp lantation. To investigate the hemodynamic factors modulating its release an d the eventual role of ADM in blood pressure regulation: after heart transp lantation, seven matched heart-transplant recipients (Htx) and seven normal subjects performed a maximal bicycle exercise test while monitoring for he art rate, blood pressure, and circulating ADM. Baseline heart rate and syst emic blood pressure were higher in Htx; left ventricular mass index and ADM tended to be higher after heart transplantation and correlated positively in Htx (r = 0.79, P = 0.03). As expected, exercise-induced increase in hear t rate was lower in Htx than in controls (60 +/- 11 % us. 121 +/- 14 %, res pectively) and blood pressure increase was similar in both groups. Maximal exercise increased significantly plasma ADM in both groups (from 25.3 +/- 3 .1 to 30.7 +/- 3.5 pmol/L, P < 0.05 and from 15.2 +/- 1.4 to 29.1 +/- 4.4 p mol/L, P = 0.02 in Htx and controls, respectively), the hypotensive peptide level remaining elevated until the 30th min of recovery. A significant inv erse relationship was observed between peak mean blood pressure and circula ting ADM in Htx (r = -0.86, P < 0.02). Besides showing that circulating ADM is increased after heart transplantation, the present study demonstrates a positive relationship between baseline ADM and left ventricular mass index . Furthermore, maximal exercise-induced increase in ADM is inversely relate d to mean blood pressure in Htx, suggesting that ADM might participate in b lood pressure regulation during exercise after heart transplantation.