endothelin-1 and Death--Sudden

A series of novel compounds bearing a 3-(1H-indol-3-yl)pyrazole-5-carboxylic acid nucleus were synthesized. Analytical and spectral data confirmed the structures of the new compounds. The structures of the regioisomers in this series were determined by (1)H-NMR spectra. The title compounds were evaluated for their endothelin-1 antagonist activities. In the in vitro functional assay, compounds 23, 24, 28 and 29 exhibited significant efficacy at the concentration of 1 μg/mL, and compounds 5b, 5c, 26 and 28 were as potent as the positive control bosentan at high concentration. In the experiment to assess prevention of endothelin-1-induced sudden death in mice, compound 5b showed comparable activity to bosentan, and 30 was more potent than bosentan. The final compounds were also screened for antibacterial activity against four Gram-positive and -negative bacteria. Some of the tested compounds showed weak antibacterial activity.

Topics: Animals; Anti-Bacterial Agents; Aorta, Thoracic; Death, Sudden; Endothelin-1; Gram-Negative Bacteria; Gram-Positive Bacteria; In Vitro Techniques; Male; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Molecular Structure; Pyrazoles; Rats; Rats, Sprague-Dawley; Structure-Activity Relationship; Vasoconstriction; Vasodilator Agents

We investigated the profiles of sudden death and hemoconcentration induced by endothelin-1 (ET-1) and big endothelin-1 (big ET-1) in mice using various compounds as pharmacological tools. In ET-1-induced sudden death (5 nmol/kg, i.v.), pretreatment with the Ca(2+)-channel blockers, diltiazem, nifedipine or verapamil at a dose of 2 mg/kg, i.v. significantly inhibited the mortality and prolonged the latency to death. These Ca(2+)-channel blockers, however, failed to inhibit the rise in hematocrit (Ht), namely hemoconcentration, induced by ET-1 (2.5 nmol/kg). A beta-adrenoceptor agonist, isoproterenol (1 mg/kg) tended to prolong the latency, whereas, a beta-adrenoceptor blocker, propranolol (2 mg/kg), and an alpha- and beta-adrenoceptor blocker, labetalol (5 mg/kg), aggravated the sudden death. Esculetin (10 mg/kg) and fenbufen (10 mg/kg), which are enzyme inhibitors in the arachidonate cascade, prevented only the hemoconcentration. Anti-arrhythmic drugs, lidocaine (1 mg/kg) and disopyramide (20 mg/kg) did not improve any parameters. Big ET-1 also caused sudden death (20 and 25 nmol/kg, i.v.) and hemoconcentration (10 nmol/kg, i.v.). Of several proteinase inhibitors, only a metalloproteinase inhibitor, phosphoramidon (2 mg/kg i.v.), prevented the sudden death and the hemoconcentration induced by big ET-1 but not by ET-1. Ca(2+)-channel blockers exerted their protective effects only when a lower dose of big ET-1 was employed. These results indicate that the sudden death caused by both peptide is mainly due to myocardial ischemia and respiratory disorder, and that hemoconcentration caused by them is due to their vasoconstrictor action but to their effects on the vascular permeability via secondary endogenous factors.

Topics: Adrenergic alpha-Antagonists; Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Animals; Aorta; Aspartic Acid Endopeptidases; Calcium Channel Blockers; Cattle; Death, Sudden; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Hematocrit; Humans; Male; Metalloendopeptidases; Mice; Mice, Inbred ICR; Protease Inhibitors; Protein Precursors

The effects of metal chelators on endothelin (ET)-converting enzyme (ECE) activity in vivo were examined. Three compounds, (2,3-dimercapto-1-propanol (DMP), toluene-3,4-dithiol (TDT) and 8-mercaptoquinoline (8-MQ)), which inhibited ECE in in vitro studies, exhibited inhibitory activity towards big ET-1-induced sudden death in mice, while EDTA did not. Similar results were obtained in big ET-1-induced hypertension. Big ET-1-induced hemoconcentration was inhibited by pretreatment with 8-MQ or EDTA but not with DMP or TDT. The elevation of immunoreactive ET-1 (IR-ET-1) in plasma after administration of big ET-1 was inhibited by pretreatment with the three compounds but not by EDTA. On the other hand, no chelator inhibited the elevation of IR-ET-1 in lung tissue after injection of big ET-1. Taking into consideration the in vitro results, more selective chelating activity of the compounds towards Zn2+ rather than Ca2+ and Mg2+ may contribute to the inhibition of big ET-1-induced responses in vivo. The ET-1 formation involved in big ET-1-induced hemoconcentration may have different physiological characteristics from that involved in big ET-1-induced sudden death or hypertension.

Topics: Animals; Aorta, Thoracic; Aspartic Acid Endopeptidases; Blood Pressure; Chelating Agents; Death, Sudden; Dimercaprol; Edetic Acid; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Glycopeptides; Hematocrit; Lung; Male; Metalloendopeptidases; Mice; Mice, Inbred ICR; Muscle Contraction; Muscle, Smooth, Vascular; Protein Precursors; Quinolines; Rats; Rats, Sprague-Dawley; Toluene

The lethal activity of big endothelin-1 (bET-1) was examined in mice and compared with endothelin-1 (ET-1). Like ET-1, intravenous administration of bET-1 produced sudden death with an approximate LD50 value at 21.0 nmol/kg, higher than that of ET-1 (3.8 nmol/kg). At doses above the respective LD90 value, the latency to death was much longer in bET-1-treated mice with sustained elevation of plasma immunoreactive ET-1 (IR-ET-1). A metalloproteinase inhibitor, phosphoramidon, although failing to inhibit sudden death induced by ET-1, suppressed bET-1-induced lethality and elevation of plasma IR-ET-1 probably due to an inhibition of the enzymatic conversion of bET-1 to ET-1.

Topics: Animals; Chromatography, High Pressure Liquid; Death, Sudden; Drug Antagonism; Endothelin-1; Endothelins; Glycopeptides; Immunoenzyme Techniques; Male; Metalloendopeptidases; Mice; Mice, Inbred ICR; Protein Precursors