title: Influence of endothelium and nitrovasodilators on free thiols and disulfides in porcine coronary smooth muscle.
abstract: It is hypothesised that the well known development of tolerance to the vasodilating action of organic nitrates is contributed by intracellular depletion of free thiols occurring during repeated treatment with these drugs. Therefore, ring segments of porcine coronary arteries with and without endothelium were treated for 30 min with either vehicle or 100 microM of isosorbide-5-mononitrate, glyceryl trinitrate, S-nitroso-N-acetyl-D,L-penicillamine or N-(3-nitratopivaloyl)-1-cysteine-ethylester (SPM 3672), and the content of histochemically stained free thiols (-SH) and disulfides (S-S-) was measured densitometrically in single smooth muscle cells. In the presence of endothelium the content of -SH in smooth muscle cells of controls (n = 8) gave an extinction of 0.127 +/- 0.013 in the intima and 0.120 +/- 0.010 in the media. The corresponding values for S-S- were 0.684 +/- 0.084 and 0.535 +/- 0.120 (n = 8). Removal of endothelium reduced S-S- to 82.1 +/- 70% and increased -SH to 126.7 +/- 6.7%. Treatment with all nitrates reduced -SH in intact artery segments to a similar degree, ranging between 54.0 +/- 4.4 and 68.7 +/- 4.7% (n = 8-10). In contrast, S-S- content was less affected and reached values between 70.6 +/- 2.8 and 91.6 +/- 6.0% (n = 8-9). As evaluated by tension studies, tolerance developed for glycerol trinitrate and isosorbide-5-mononitrate but not for S-nitroso-N-acetyl-D,L-penicillamine. Induction of tolerance with glycerol trinitrate (0.1 mM) produced a significantly more pronounced attenuation in activity of isosorbide-5-mononitrate than tolerance induction with isosorbide-5-mononitrate (1 mM). In contrast, the potency of SPM 3672 was not reduced in glycerol trinitrate-tolerant arteries. We conclude that, in porcine coronary arteries, an intact endothelium modifies intracellular thiols and disulfides. In addition, nitrate tolerance is associated with, but probably not caused by, thiol depletion.
authors.affiliation: Institut für Pharmakologie, Heinrich-Heine Universität, Düsseldorf, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Kojda
authors.forename: W
authors.initials: W
authors.lastname: Meyer
authors.forename: E
authors.initials: E
authors.lastname: Noack
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects* / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D004220:Disulfides / Q000378:metabolism*; D004361:Drug Tolerance; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006651:Histocytochemistry; D066298:In Vitro Techniques; D007548:Isosorbide Dinitrate / Q000031:analogs & derivatives / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology; D005996:Nitroglycerin / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D004220:Disulfides; D009566:Nitrates; D013438:Sulfhydryl Compounds; D014665:Vasodilator Agents; C083079:N-(3-nitratopivaloyl)cysteine ethyl ester; D005996:Nitroglycerin; D007548:Isosorbide Dinitrate; D003545:Cysteine; C030397:isosorbide-5-mononitrate