USEFULNESS OF INCREASED MYOCARDIAL CYCLIC ADENOSINE-3',5'-MONOPHOSPHATE CONTENT AS A SIGN OF REJECTION AFTER CARDIAC TRANSPLANTATION

Cardiac allograft rejection represents ct series of cellular and molec ular events triggered by the recognition of the graft by the host immu ne system. One of the second messenger systems involved in mitogenic m echanisms is the cyclic adenosine 3',5'-monophosphate (cAMP)-coupled s ignaling system. The aim of this preliminary study was to evaluate whe ther rejection after cardiac transplantation is accompanied by changes in the expression of cAMP. Myocardial cAMP content was determined by radioimmunoassay in endomyocardial biopsy specimens taken during routi ne follow-vp after cardiac transplantation with or without cellular an d/or vascular (i.e., coronary vasculopathy) rejection, respectively. A nalysis of the different subgroups of patients showed that patients wi thout any signs of rejection (no vasculopathy, no cellular rejection) had the lowest myocardial cAMP content (1.41 +/- 0.12 pmol/mg wet weig ht). Patients with either cellular or vascular rejection had significa ntly higher myocardial cAMP levels (2.25 +/- 0.29 and 2.24 +/- 0.59 pm ol/mg wet weight, respectively, p <0.05). Patients with both cellular rejection and coronary vasculopathy had the highest cAMP levels (5.95 +/- 1.6 pmol/mg wet weight; p <0.001). We speculate that cAMP may play a functional role in mediating rejection induced by mitogenic factors activated after cardiac transplantation, suggesting a possible ''cros s-talk'' between different cellular signaling pathways.