CHANGES IN PLASMA-VOLUME REGULATING MECHA NISMS IN RENAL-TRANSPLANT PATIENTS WITH OR WITHOUT CYCLOSPORINE-A - ROLE OF CYCLIC GUANOSINE-MONOPHOSPHATE AND ATRIAL-NATRIURETIC-PEPTIDE

In the present study in transplant patients, treated with or without C yclosporin A (CsA), we examined the changes in the renal plasma volume -regulating mechanisms involving cyclic guanosine monophosphate (GMPc) and atrial natriuretic peptide (PNA). Manoeuvres that either decrease (furosemide administration) or increase (saline infusion) the extrace llular volume were used to challenge the sodium and volume regulatory systems. The results disclosed several characteristics of the transpla nt patients, from the point of view of the cGMP/PNA-dependent mechanis ms, as follows urinary cGMP levels were higher in the transplant patie nts compared with controls. Plasma cGMP, however, was higher in non Cs A-treated patients compared to CsA patients. Both the baseline PNA and the relationship between PNA and cGMP levels were different in CsA-tr eated, compared to non CsA-treated patients. The present results offer new data concerning the PNA and GMPc levels in transplant patients an d suggest that: a) renal transplantion induces a significant variation in cGMP regulation; b) there are relevant differences in plasma cGMP and baseline plasma PNA between patients receiving or not receiving Cs A.