Increased cAMP levels in lymphocytes of allografted rats: possible relationship to delayed graft rejection

We studied the levels of nucleotides in peripheral blood and in spleen lymphocytes obtained from allografted rats. Four types of allografts were performed by using ACI rats (RT1a) as donors and Lewis rats (RT1l) as recipients: heart, pancreas, kidney and liver. Ungrafted Lewis rats were used as controls. Rejection time without immunosuppression occurred at 6.7 +/- 0.25 days from transplant in heart-allografted, at 7.3 +/- 0.25 days in pancreas-grafted, at 6.8 +/- 0.24 days in kidney-grafted, and at 20 +/- 3 days in liver-grafted rats. Biochemical assays on lymphocytes were performed on the 7th day after operation by measuring the intracellular content of APT, ADP, AMP, cAMP, NAD+ and NADH. Our results showed that the prolonged survival of allografts in liver-grafted rats correlated with the higher content of cAMP in their lymphocytes than in those of controls. In addition, ATP and ADP levels in lymphocytes from heart-and pancreas-allografted rats were significantly lower than those of lymphocytes from liver-allografted rats.