Increased endothelin-1 content in the platelets of hemodialysed patients

Patients undergoing hemodialysis, present platelets (PLTs) with physiological dysfunction. Aggregated PLTs stimulate endothelin-l (ET-1) secretion from endothelial cells. In turn, ET-1 abolishes PLT aggregation. The aim of this study was to determine any presence of ET-I in the PLTs of hemodialysed patients and to compare its levels with normal subjects. Platelets, isolated from hemodialysed patients, revealed lower aggregation (76 +/- 13%) compared with healthy subjects (96 +/- 2%). Plasma ET-1 was increased in hemodialysed patients 23.5 +/- 3.2 fmol/ml, vs. 10.9 +/- 1.6 fmol/ml in normal subjects. Immunoreactive endothelin-l was detected in the platelets of both groups. The intraplatelet ET-1 of hemodialysed patients was 13.8 +/- 3.1 fmol/mg protein, vs. 7.9 +/- 1.3 fmol/mg protein in normal individuals. Total RNA was isolated from platelets and reverse trancriptase-mediated polymerase chain reaction (RT-PCR) revealed no presence of the preproET-1 mRNA in either normal or hemodialysed platelets. This suggests that ET-1 is internalized from the plasma. In summary, platelets contain but do not express ET-1. The increased levels of ET-I in the platelets of the hemodialysed patients may be partly responsible for their lower aggregation.