Effect Of Cetiedil Research Articles

An analysis of the mechanism by which cetiedil inhibits sickling

A study has been carried out into the effects of cetiedil on the activities of Na +, K + and Ca 2+, Mg 2+ - ATPases of the normal human erythrocyte membrane. In general, cetiedil inhibits both ATPases activities but with characteristic inhibition profiles and varying degrees of efficacy. The activities were inhibited non-competitively at the cetiedil concentration which caused 50% inhibition of each enzyme. In addition, the effects of cetiedil on the transport of K + and phosphate ions across the membrane were monitored and compared. Cetiedil was found to stimulate K + release and to inhibit phosphate uptake. At low concentrations, both processes were concentration dependent. Stimulation of K + efflux reached a plateau at a concentration of 1.2 mM. The antisickling effect of cetiedil is explained mainly in the light of the changes it induces in the activities of membrane-bound ATPases and the permeability properties of the erythrocyte membrane to cations and anions.

The effects of cetiedil and its congeners on levcromakalim-stimulated 86Rb efflux from smooth and skeletal muscle

The effects of cetiedil on levcromakalim-stimulated 86Rb efflux from rat aorta, rat anococcygeus and frog sartorius muscle have been investigated. In experiments on rat aorta, cetiedil inhibited the tracer efflux stimulated by 10 μM levcromakalim with an IC 50 of 1.3±0.4 μM. In the rat anococcygeus and frog sartorius 10 μM cetiedil caused 67±11% and 84±4% inhibition of the responses to 10 μM and 50 μM levcromakalim respectively. The effect of two analogues of cetiedil, UCL 1285 (cetiedil methiodide) and UCL 1495 (triphenyl acetic acid-2- N[5-ethyl-2-methylpiperidinoethyl] ester) were also tested on rat aorta. UCL 1285 caused inhibition of the response to 10 μM levcromakalim with an IC 50 of approximately 6 μM. In contrast, UCL 1495 (10 μM) had no significant effect. It is concluded that cetiedil is an effective blocker of the action of levcromakalim in smooth and skeletal muscle but does not distinguish between tissues. The relative activities of cetiedil, UCL 1285 and UCL 1495 are discussed in relation to their activity at other cetiedil-sensitive K + channels.

Inhibition of Erythrocyte Calcium Transport by Cetiedil

The elevated calcium content found in red cells from patients with sickle cell anemia may be of pathophysiologic importance in the hemolysis and vasoocclusion which characterize this disorder. Cetiedil, an antisickling agent, has been reported to inhibit the activity of enzymes that are stimulated by the calcium regulatory protein calmodulin. To investigate the mechanism by which cetiedil modifies calcium-mediated erythrocyte function, the effect of the drug on the active transport of calcium into inside-out erythrocyte vesicles was examined and its influence on the activities of phosphodiesterase and Ca-ATPase studied. Cetiedil, in the presence of calmodulin, significantly inhibited calcium transport into inside-out vesicles that were prepared with erythrocytes from normal controls and from patients with sickle cell anemia. However, in the absence of calmodulin, no inhibition was observed. Likewise, cetiedil inhibited calmodulin-stimulated, but not basal, activities of phosphodiesterase and Ca-ATPase. These data, along with previous reports, suggest that cetiedil does not act by lowering the intracellular calcium content. It is, therefore, likely that the beneficial effect of cetiedil is due to its ability to protect the red cell from the deleterious consequences of an elevated concentration of intracellular calcium.

Cetiedil, a drug that inhibits acetylcholine release in Torpedo electric organ.

The effects of cetiedil, a vasodilatator substance with reported anticholinergic properties, were examined on cholinergic presynaptic functions at the nerve electroplaque junction of Torpedo marmorata using either synaptosomes or slices of intact tissue. Cetiedil abolished the calcium-dependent release of acetylcholine (ACh) triggered by depolarization or by addition of A23187 ionophore, a finding localizing the site of action downstream from the calcium entry step. In addition, a direct effect on the release process itself was indicated by the observation that cetiedil blocks the release of ACh mediated by a recently isolated presynaptic membrane protein, the mediatophore, reconstituted into ACh-containing proteoliposomes. In all three preparations, ACh release was inhibited by cetiedil with a Ki of 5-8 microM. Under the conditions used in these release experiments, the synthesis of ACh and its compartmentation within the nerve terminals were not modified. However, the drug was able to reduce high-affinity choline uptake and vesicular ACh incorporation when it was given together with the radioactive precursor, a result showing that cetiedil has a broad inhibitory action on cholinergic uptake processes.

Enhancement of conductive anion permeability in cultured cells by cetiedil

Cetiedil, a drug that is reported to block K +-channels, substantially increases the conductive Cl − permeability of Chinese hamster ovary (CHO) cells. The permeability was monitored by volume changes in cells treated with gramicidin to increase the cation permeability. Under this circumstance, increases in Cl − conductances result in volume changes detectable by electronic sizing, with the direction determined by the gradients of the permeating ions. In NaCl or KCl media, swelling occurs, but in N-methylglucamine chloride, shrinking. The increases in Cl − conductance could also be measured as an increased 36Cl − flux or by changes in membrane potential (measured by fluorescence of a potential-sensitive dye) toward the Cl − equilibrium potential. The effect of cetiedil was concentration dependent, with maximal effect at 50 μM. The anion specificity for the conductance was NO 3 − > Cl − = Br − ⪢ SO 4 −2 or isethionate. A number of other drugs that influence transport activities had no effect on Cl − conductance. The cetiedil effect on Cl − conductance was observed in one other cell line, but was absent in several other cell types. The cetiedil-induced Cl − conductance in CHO cells appears to involve a different pathway than that induced by exposure to hypotonic medium.

Effect of cetiedil on acetylcholine release and intramembrane particles in cholinergic synaptosomes.

The release of acetylcholine (ACh) from instantly frozen Torpedo electric organ synaptosomes in the course of stimulation is systematically associated with an increase in the number of large intramembrane particles counted on freeze-fracture replicas. The drug cetiedil, which is a potent inhibitor of ACh release, also blocks the increase in the number of large particles. The blockage was studied either after ionophore A 23187 or Glycera neurotoxin action in the presence of calcium.

Effect of cetiedil on the superoxide-generating system of porcine neutrophils.

Cetiedil, alpha-cyclohexyl-3-thiopheneacetic acid 2-(hexahydro-1H-azepin-1-yl)-ethyl ester, was found to inhibit the generation of superoxide (O2-) by porcine neutrophils exposed to various stimulators. The concentration of cetiedil required for 50% inhibition was about 45 microM when neutrophils were stimulated by phorbol myristate acetate. Cetiedil not only decreased the rate of generation of O2-, but prolonged the lag time prior to the production of O2-. The inhibitory effect of cetiedil on the O2(-)-generating activity of the NADPH oxidase in the membrane vesicles was less than that on whole cells; the concentration of cetiedil necessary for 50% inhibition was about 250 microM. To study the mechanism of cetiedil's effect on the membrane, the transmembrane potential of neutrophils and the intracellular free Ca2+ concentration were monitored by using fluorescence probes, diS-C3-(5), and quin-2, respectively. Cetiedil caused depolarization of the membrane potential and increased the intracellular free Ca2+. These results indicate that integrity of ionic distribution is necessary to activate the O2(-)-generating system of neutrophils.

Effects of cetiedil on the oxidative metabolism of activated polymorphonuclear leucocytes.

Cetiedil, alpha-cyclohexyl-3-thiopheneacetic acid 2-(hexahydro-lH-azepin-l-yl)-ethyl ester, was found to specifically suppress oxygen uptake by polymorphonuclear leucocytes (PMN) that were exposed to myristate or heat-killed E. coli. The chemical had no effect on the basal respiration rate of PMN in the resting state. Inhibition of oxygen uptake by cetiedil was proportionate to the degree of inhibition of the generation of O-2 and H2O2. It was also found that cetiedil suppressed the rate of the phagocytosis by PMN of opsonized oil droplets. Cetiedil had no effect on subcellular NADPH oxidase, an enzyme responsible for the respiratory burst that is activated by the perturbation of PMN plasma membrane with phagocytable particles or stimulators such as myristate. These results suggest that cetiedil affects the trigger mechanism of the plasma membrane to inhibit the activation of NADPH oxidase.

Effect of cetiedil on cation and water movements in erythrocytes.

Cetiedil is a potential antisickling agent whose major effect appears to be at the erythrocyte membrane. To test the hypothesis that cetiedil alters cation transport, we studied the effect of the drug in promoting changes in cell water (Wc), cell sodium (Nac), and cell potassium (Kc). Results are quite different depending on the presence or near absence of intracellular ATP. With fresh cells, 100 microM cetiedil causes little in the net cation or water movements compared with control cells incubated for 2 h. At cetiedil concentrations greater than 100 microM, however, net movements of sodium and potassium increase considerably, and cell swelling results from a net Nac gain that exceeds a net Kc loss. All water movements can be accounted for by cetiedil-induced net cation movements. When 100 microM ouabain is added along with cetiedil, net Nac gain, net Kc loss, and net Wc gain are all increased compared with results obtained with cetiedil alone. External calcium inhibits cetiedil-induced changes in cation transport. With cells depleted of their ATP, cetiedil inhibits the typical potassium loss that occurs in the presence of external calcium; net sodium uptake changes little under these conditions, regardless of the presence or absence of external calcium. Our findings indicate a complex mode of action for cetiedil on the erythrocyte membrane, and support the hypothesis that the erythrocyte membrane, and support the hypothesis that the antisickling effect of the drug observed in vitro results from dilution of intracellular hemoglobin secondary to net salt and water gain.

Effect of cetiedil, an in vitro antisickling agent, on erythrocyte membrane cation permeability.

Cetiedil has been reported to relieve painful crises in sickle cell anemia and to have antisickling properties in vitro. The drug alters neither oxygen affinity nor the solubility of deoxyhemoglobin S. Because the viscosity of the erythrocyte interior and the kinetics of gelation are dependent on the concentration of hemoglobin, we postulated that cetiedil might inhibit sickling by modifying erythrocyte sodium or potassium movements in a manner that would increase cell water content and thus dilute the cell hemoglobin. The drug has two such effects: it inhibits the specific increase in potassium permeability that follows a rise in cytoplasmic calcium concentration and it causes a rise in passive sodium movements. These effects are further evidence that cell ion and water movements may be important in the process of sickling and suggest a mechanism for the results reported with cetiedil.

Effect of cetiedil, an in vitro antisickling agent, on erythrocyte membrane cation permeability.

Effect of cetiedil, an in vitro antisickling agent, on erythrocyte membrane cation permeability.