TRAINING EFFECTS ON THE HYDROMINERAL ENDOCRINE RESPONSES OF CARDIAC TRANSPLANT PATIENTS

Cardiac transplant patients manifest several haemodynamic changes as w ell as altered peripheral responses to exercise which may disrupt body fluid regulation. This study examined the effect on an endurance trai ning programme on the exercise-induced hydromineral endocrine response s of heart transplant patients. Seven patients underwent a square-wave exercise test before and after a 6-week training programme. The tests were performed at the same absolute intensity but, during training, t he workload was increased to maintain the same relative exercise inten sity. Pretraining results were compared to those obtained from age-mat ched controls. Training improved physical capacity, producing a signif icant increase in maximal tolerated power and workload between the fir st and last training session (P < 0.05, P < 0.001, respectively). Haem atocrit and osmolality were increased in both groups at the end of exe rcise (P < 0.01) but changes observed post-training did not differ fro m pretraining values. Apart from atrial natriuretic peptide (ANP), whi ch showed significantly higher concentrations at rest and during exerc ise (P < 0.01), the changes in hydromineral hormones of the patients r esembled those of the controls. Basal plasma renin activity (PRA) was slightly raised prior to training (P < 0.07) compared to the controls and post-training. For both PRA and aldosterone, a significant trainin g effect was revealed when both the exercise-stimulated increase and p ostexercise decline were considered (P < 0.05), possibly reflecting lo wer noradrenaline concentrations. Training had no effect on either bas al or exercise stimulated ANP levels, which is compatible with the the ory that ANP regulation is largely under mechanical rather than sympat hetic nervous system control. Mean arginine vasopressin concentrations in the patients were not increased, possibly due to inhibitory effect s of immunosuppressive glucocorticoids combined with the large variati on in response observed, particularly for the untrained patients. In s ummary, these results showed that despite cardiac denervation, the hea rt transplant patients demonstrated effective body fluid regulatory en docrine responses during exercise and that although training produced substantial improvement in their physical capacity, it was accompanied by only subtle changes in hydromineral hormones.