REDUCTION OF RENAL FUNCTIONAL RESERVE IN KIDNEY-TRANSPLANT RECIPIENTS- A POSSIBLE ROLE OF ARACHIDONIC-ACID METABOLISM ALTERATIONS

Aim: Renal functional reserve (RFR), resulting from an increase in glo merular filtration (GFR) after protein load, is a matter of debate. In kidney transplant recipients most studies have failed to show conclus ive results, reporting either the absence, the reduction or the presen ce of renal reserve in normo-functioning kidneys. The aim of this stud y was to investigate RFR in kidney transplant patients as well as the possible hormonal vasoactive alterations underlying the reduction of r enal reserve reported in some patients. Patients and methods: We studi ed 8 controls and 25 patients, the latter with no history of acute rej ection for at least 12 months and GFR >50 ml/min. The 25 patients were divided into 2 groups based on the presence (10) or the absence (15) of RFR. Results: Both the RFR group and the controls experienced a sim ilar increase of GFR after oral protein load: 24.3 +/- 15.57% vs 24.4 +/- 10.8%. The group without RFR showed a paradoxical reduction of GFR after oral protein load: 13.3 +/- 13.2% (p <0.001). We analyzed the f iltration fraction (FF) and observed that the group without RFR had hi gher values than the group with RFR and the controls: 0.35 +/- 0.11 vs 0.29 +/- 0.07 (p = 0.01) and vs 0.26 +/- 0.02 (p = 0.04). The hyperfi ltration state observed in the group without RFR was sustained by a hi gh level of thromboxane. The urine ratio TxB2/6ketoPgF1 alpha was high er in the group without RFR than in the RFR group 0.78 +/- 0.2 vs 0.64 +/- 0.1 (p = 0.01). This ratio decreased only in the RFR group after a meat meal. In all the patients, changes of TxB2/6ketoPGF1 alpha were inversely correlated to changes of GFR after a meat meal (r = -0.6, p = 0.01). Conclusions: In conclusion, these data demonstrate that kidn ey transplant recipients with good organ function can be grouped accor ding to the presence of RFR. RFR appears to be inversely correlated wi th the TxB2/6ketoPGF1 alpha ratio, and its decrease seems to be Linked to the failure of thromboxane to decrease and prostacycline to increa se after a meat meal.