CHARACTERIZATION OF A PEPTIDE ENDOTHELIUM-DERIVED CONSTRICTING FACTOREDCF

Endothelium regulates vascular tone by the release of dilator and cons trictor mediators. Among the latter, besides endothelin, an 'endotheli um derived constricting factor' EDCF sensitive to cyclooxygenase-inhib itors has been described. The aim of this study was to clarify the nat ure of this EDCF. Eluate from porcine aortic segments or supernatants (crude extracts) of porcine aortic segments were each tested for vascu lar effects in a bioassay system consisting of two endothelium-denuded acceptor vessels (rabbit abdominal aorta) before or after treatment w ith trypsin. The donor vessels were incubated with physiological salin e solution with or without treatment with cycloheximide, quinacrine or indomethacine. Ultrafiltrates and fractions of a gelfiltration of the supernatants were also tested and compared with SDS-PAGE of these ext racts. Finally, porcine aortic endothelial cells (PAEC) were cultured and the supernatant compared with that of the native aortae. A vasocon strictive factor was released from the luminal surface of the porcine aortic segments, which if infused into the rabbit aortas induced two s ucceeding vasoconstrictions of 15-20 min duration each (the first 20 m in after the first of extract-infusion, the second after 50 min) reach ing 7% amplitude of a 0.2 mu mol l(-1) norepinephrine-induced constric tion. These constrictions were enhanced if the crude extract of the po rcine aortae was concentrated. This constricting factor was a protein with an approximative molecular weight of 9.000 Da. The release of thi s factor was insensitive to cycloheximide pretreatment indicating no d e novo synthesis. However, the release of the factor could be markedly (50%) depressed by pretreatment with either quinacrine or indomethaci ne. The factor was not released from cultured PAEC. From these results , we conclude, that besides endothelin, endothelium luminally can rele ase another endothelium-derived constricting factor named EDCF, a pept ide with a molecular weight of 9.000 Da, which is not identical to end othelin and can induce long lasting vasoconstrictions. The release or synthesis of that EDCF seems to depend on cyclooxygenase and phospholi pase A(2) activity. We, thus, propose the name PLA(2)-sensitive EDCF f or that factor. (C) 1997 The Italian Pharmacological Society.