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1.
Br J Pharmacol ; 113(2): 379-84, 1994 Oct.
Article in English | MEDLINE | ID: mdl-7834187

ABSTRACT

1. Verapamil and emopamil are structurally related phenylalkylamine calcium channel/5-HT2 receptor antagonists that differ in their anti-ischaemic properties in experimental studies. The quaternary ammonium derivatives of these compounds were prepared and tested in assays of neuronal voltage-sensitive calcium channel (VSCC) function to determine whether the compounds act at intra- or extracellular sites. 2. The compounds were tested in K(+)-evoked: (1) rat brain synaptosomal 45Ca2+ influx, (2) release of [3H]-D-aspartate from rat hippocampal brain slices and (3) increase of intracellular calcium in rat cortical neurones in primary culture. 3. Verapamil, emopamil and the emopamil quaternary derivative caused concentration-dependent and comparable (IC50 values approximately 30 microM) inhibition of synaptosomal 45Ca2+ influx and [3H]-D-aspartate release. The verapamil quaternary derivative was considerably less active in these assays (IC50 > 300 microM). 4. The evoked increase of intracellular calcium in cortical neurones was inhibited with the following rank order of potency (IC50 value, microM): emopamil (3.6) > verapamil (17) > emopamil quaternary derivative (38) > verapamil quaternary derivative (200). 5. The results suggest that verapamil and emopamil inhibit nerve terminal VSCC function (synaptosomal 45Ca2+ influx and [3H]-D-aspartate release) by acting at distinct intracellular and extracellular sites, respectively. Verapamil and emopamil may inhibit cell body VSCC function (evoked increase of intracellular calcium in neocortical neurones) by acting at both intracellular and extracellular sites. 6. The different 'sidedness' of action of emopamil and verapamil on nerve terminal VSCC function and/or the preferential inhibition of cell body VSCC function by emopamil may at least partially explain the relatively greater neuroprotective efficacy of emopamil in experimental models of ischaemia.


Subject(s)
Aspartic Acid/metabolism , Calcium Channel Blockers/pharmacology , Calcium/metabolism , Neurons/metabolism , Verapamil/analogs & derivatives , Animals , Calcium Radioisotopes , Electrophysiology , Hippocampus/drug effects , Hippocampus/metabolism , In Vitro Techniques , Neurons/drug effects , Potassium/pharmacology , Rats , Synaptosomes/drug effects , Synaptosomes/metabolism , Verapamil/pharmacology
2.
J Assoc Off Anal Chem ; 59(5): 1185-6, 1976 Sep.
Article in English | MEDLINE | ID: mdl-965343

ABSTRACT

A rapid method is described for the determination of the growth regulator ethephon (2-chloroethyl phosphonic acid) in tomatoes. Samples are extracted with ethyl acetate. The extract is methylated, decolorized with carbon, and analyzed by gas-liquid chromatography on a column packed with 15% QF-1/10% DC-200 on Chromosorb W (HP). A flame photometric detector is used. Recoveries from tomatoes fortified with 0.1-11.0 ppm ethephon were 78-98%. The sensitivity of this method is about 0.1 ppm.


Subject(s)
Organophosphorus Compounds/analysis , Plant Growth Regulators/analysis , Vegetables/analysis , Chromatography, Gas/methods , Chromatography, Liquid , Ethyl Chloride/analogs & derivatives , Ethyl Chloride/analysis
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