Blunted humoral responses to mental stress and physical exercise in cardiac transplant recipients

Since recent results have suggested that the relative neuroendocrine response to physical activity is exaggerated following cardiac transplantation, we studied the haemodynamic-neuroendocrine responses to mental stress, and to physical exercise, in heart transplant recipients free of antihypertensive medication. Ten patients were studied 1.7 years (mean) after transplantation and compared with 10 age-matched controls. Plasma levels of catecholamines, renin activity, aldosterone, atrial natriuretic factor, calcitonin gene-related peptide (CGRP), and endothelin were measured, together with blood pressure and heart rate, during mental stress and graded, submaximal ergometry. Mental stress increased blood pressure in both groups (P < 0.02), but heart rate in controls only (P < 0.05). Noradrenaline did not change. Adrenaline rose in controls only (P < 0.05). Plasma renin activity increased in both groups (P < 0.02), while aldosterone increased in controls only P < 0.02). Atrial natriuretic factor, and endothelin were higher in patients (P < 0.01). Mental stress, however, did not induce any changes. No significant differences were found in relative changes (delta %), except for plasma renin activity which was greater in controls (P < 0.05). During ergometry, only delta % noradrenaline was greater in patients (P < 0.05). delta % for all other parameters were either of the same order as in controls, or blunted. Thus, apart from noradrenaline, cardiac transplant recipients, not receiving antihypertensive medication, do not show an exaggeration in the relative neuroendocrine response to mental or physical stress.