Cocaine Increases the Endothelial Release of Immunoreactive Endothelin and Its Concentrations in Human Plasma and Urine: Reversal by Coincubation With σ-Receptor Antagonists

Background —Cocaine-associated vascular events are not completely explained by adrenergic stimulation. The purposes of this study were to investigate whether vasoconstrictive endothelin-1 is released by cocaine and to elucidate the mechanisms involved. Methods and Results —Endothelin-1 was measured by radioimmunoassay and high-performance liquid chromatography (1) in the supernatant of porcine aortic endothelial cells after treatment with cocaine (10 −7 to 10 −4 mol/L) and a σ-receptor antagonist, haloperidol (10 −6 mol/L) or ditolylguanidine (10 −5 mol/L) and (2) in plasma and urine of 12 cocaine-intoxicated patients and 13 healthy control subjects. Radioligand binding assays were performed on endothelial membrane preparations. In cell culture, cocaine significantly increased endothelin accumulation above baseline at 3 to 24 hours; endothelin release rates per hour increased dose-dependently, reaching a plateau of 175±23% of control at hour 4 to 5. Coincubation of cocaine with haloperidol or ditolylguanidine abolished or reduced cocaine-induced endothelin release. Endothelial membrane preparations specifically and displaceably bound the highly selective σ-ligand [ 3 H]ditolylguanidine (25×10 −9 mol/L), with 1400 binding sites estimated per cell. Endothelin-1 levels in plasma (22.7±5.6 versus 7.3±0.8 pmol/L) and urine (41.5±10.1 versus 12.7±3.8 pmol/L) of cocaine-intoxicated patients were significantly increased compared with control values. Conclusions —The data suggest that cocaine increases the endothelin-1 release in vitro and in vivo. The cocaine-induced vasoconstriction/vasospasm may therefore be facilitated by the release of endothelin-1. Cocaine appears to be an exogenous stimulator at endothelial σ-receptors. The endogenous ligands of this antiopioid system may prove to play a role in vasospastic angina, acute myocardial infarction, and sudden cardiac death.