iloprost and cicletanine

10 years ago a now 49-year-old woman with Render-Osler-Weber disease showed unspecific symptoms of nausea, and general unwellness. Pulmonary manifestation of the disease was accompanied by pulmonary hypertension.. Teleangiectasia of the tongue and pharynx as well as of the mucosa of mouth and nose were observed. Fixed-splitting of the second heart sound with accentuated pulmonary component and a 2/6 systolic murmur over the tricuspid valve were heard. In addition, a murmur was heard dorsal over the right lung's lower lobe. Apart from minor oedema of both ankles, the physical status was not remarkable. Echocardiography showed dilatation of the right ventricle and a minor regurgitation of the tricuspid valve. The computed tomography showed dilatation of the pulmonary arteries as well as an arteriovenous malformation in the right lower lobe. Right-heart catheterisation revealed elevated pulmonary pressure. THERAPY AND FOLLOW-UP: Initial treatment with a calcium channel blocker proved insufficient and was changed to inhalative, and later to oral prostanoids. Under this treatment the cardiopulmonary state was stabilised, but episodes of epistaxis were increased. Two years after readjustment of the medication to a dual endothelin receptor antagonist, the cardiopulmonary state remains stable without significant haemorrhagic complications.. Prostanoid treatment in patients with Render-Osler-Weber disease and additional pulmonary hypertension can lead to an increased risk of haemorrhagic complications. Treatment with newer medications, such as endothelin receptor antagonists, seems indicated as successfully illustrated in our case.

Topics: Anticoagulants; Antihypertensive Agents; Bosentan; Calcium Channel Blockers; Diuretics; Endothelin Receptor Antagonists; Epistaxis; Epoprostenol; Female; Furosemide; Humans; Hypertension, Pulmonary; Iloprost; Middle Aged; Nifedipine; Pedigree; Phenprocoumon; Pyridines; Sulfonamides; Telangiectasia, Hereditary Hemorrhagic; Treatment Failure; Vasodilator Agents

1. Numerous compounds and changes in physical state functions shift the membrane potential of vascular smooth muscle to more negative values. The consequence is a vasodilatation because Ca2+ channels are closed. K+ channel opening frequently causes the hyperpolarization. 2. Acidification of the blood substitute solution and a fall in O2 partial pressure dilate arterial vessels. Acidosis is associated with a rise in K+ permeability and a simultaneous fall in Na+ permeability. Prostacyclin has a 20-30% share, and EDHF a 70-80% share, in hypoxic vasodilatation. Experiments with iloprost (PGI2 analogue) confirmed the K+ channel opening properties of this drug. A voltage-dependent K+ channel and a Ca(2+)-activated K+ channel, via the influence of cA-PK or cG-PK, are responsible for the hyperpolarization with iloprost and with oxygen deficiency. 3. Cicletanine and ajoene cause a concentration-dependent membrane hyperpolarization and are potent vasodilators. A cicletanine concentration, which is attained by the dosage given to patients, is sufficient to produce these effects. Ajoene exerts a hyperpolarizing and vasodilating influence even in a concentration which may occur in the extracellular space by the administration of a single garlic clove. 4. The stationary activation curve 'developed force vs. membrane potential' satisfactorily explains the effects of K+ channel openers. The tight electromechanical coupling expressed by this curve comprises a 50% vasorelaxation for a 2.5 mV hyperpolarization. In the linear part of the curve, the coupling ratio is 5.1 mV/g. 5. In the vascular smooth muscle, vasorelaxation can be evoked by membrane hyperpolarization which is linked to a simultaneous increase in K+ outward current and 42K+ efflux. In the case of substances whose influence is solely or partially receptor-mediated, cyclic nucleotides may be involved in vasorelaxation. Since cyclic nucleotides also hyperpolarize through an increase in K+ conductance, the resulting dilatation often cannot be divided into its single components. Therefore, it is sensible not to give the term "K+ channel opener" too fine a definition. The term should be applied to all substances and changes in physical states which predominantly increase the open probability of K+ channels finally via a conformational change in the cell membrane. For example, giving an acidic blood substitute solution (acidosis) is an intervention opening K+ channels. Which K+ channel and which single channel cond

Topics: Animals; Antihypertensive Agents; Basilar Artery; Carotid Arteries; Coronary Vessels; Diuretics; Dogs; Endothelium, Vascular; Iloprost; In Vitro Techniques; Indomethacin; Membrane Potentials; Muscle Contraction; Muscle, Smooth, Vascular; Oxidopamine; Portal Vein; Potassium Channels; Pyridines; Rabbits; Rats; Rats, Inbred Strains; Vasodilation

1) Numerous compounds and changes in physical state functions shift the membrane potential of vascular smooth muscle to more negative values. The consequence is a vasodilatation because Ca2+ channels are closed. K+ channel opening frequently causes the hyperpolarization. 2) Acidification of the blood substitute solution, a fall in O2 partial pressure, and an increase in blood flow dilate arterial vessels. Acidosis is associated with a rise in K+ permeability and a simultaneous fall in Na+ permeability. Prostacyclin has a 20-30% share, and EDHF a 70-80% share in hypoxic vasodilatation. Experiments with iloprost (PGI2 analogue) confirmed the K+ channel opening properties of this drug. A voltage-dependent K+ channel and a Ca(2+)-activated K+ channel, via the influence of cA-PK or cG-PK, are responsible for the hyperpolarization with iloprost and with oxygen deficiency. 3) With 23Na+ nuclear magnetic resonance techniques, it has been demonstrated that with flow-dependent vasodilatation, proteoheparan sulphate integrated in the membrane of endothelial cells possibly served as a "flow sensor". With an external strain, such a compound can go from a randomly coiled state to an oriented state. Based on these viscoelastic properties, heparan sulphate proteoglycan is present as a random coil under "no flow" conditions and as an unfurled filament structure with increasing flow. This conformational change produces additional anionic binding sites to which Na+ ions of the blood are bound. A membrane hyperpolarization could be directly initiated by this Na+ binding via the protein fraction within the macromolecule or via a change in zeta-potential. Therefore, these ions can trigger the signal transduction for a vasodilatory vessel reaction. Decrease in flow is followed by a structural change of the macromolecule towards coil conformation, a release of Na+ ions and, thus, an interruption of the signal chain. 4) Cicletanine, aqueous garlic extract, and ajoene cause a concentration-dependent membrane hyperpolarization and are potent vasodilators. A cicletanine concentration, which is attained by the dosage given to patients, is sufficient to produce these effects. Under noradrenaline, the cicletanine effect is amplified. Aqueous garlic extract and ajoene exert a hyperpolarizing and vasodilating influence even in a concentration which may occur in the extracellular space by the administration of a single garlic clove. 5) The stationary activation curve "developed force vs.

Topics: Animals; Antihypertensive Agents; Calcium; Culture Techniques; Diuretics; Dogs; Endothelium, Vascular; GTP-Binding Proteins; Iloprost; Magnetic Resonance Spectroscopy; Membrane Potentials; Muscle, Smooth, Vascular; Norepinephrine; Oxygen Consumption; Potassium Channels; Pyridines; Rabbits; Rats; Rats, Inbred Strains; Second Messenger Systems; Sodium Channels; Vasodilation