ABSTRACT
Anticholinergic activity of a number of tricyclic antidepressives and nomifensine was demonstrated and their order of affinity for the cholinergic receptors of rat jejunum was determined. The influence of ethinyl estradiol and a conjugated estrogen product, Premarin on the binding of several tricyclic antidepressives to the hepatic mixed function oxidase system was investigated. The influence of these steroids on the metabolism of the antidepressives was evaluated and ethinyl estradiol was shown to have a marked influence on the metabolism of the antidepressives studied, while conjugated estrogens were shown to have little effect.
Subject(s)
Antidepressive Agents, Tricyclic/administration & dosage , Estrogens, Conjugated (USP)/administration & dosage , Ethinyl Estradiol/administration & dosage , Liver/metabolism , Receptors, Cholinergic/metabolism , Animals , Antidepressive Agents, Tricyclic/metabolism , Drug Interactions , Female , Jejunum/metabolism , Microsomes, Liver/metabolism , Mixed Function Oxygenases/metabolism , Nomifensine/administration & dosage , Rats , Rats, Inbred StrainsSubject(s)
Anti-Bacterial Agents/pharmacology , Cell Membrane Permeability , Cell Membrane/metabolism , Lipid Metabolism , Membranes, Artificial , Proteins/metabolism , Acholeplasma laidlawii , Amphotericin B/pharmacology , Cations, Divalent/metabolism , Cations, Monovalent , Cell Membrane/drug effects , Cell Membrane/ultrastructure , Cell Membrane Permeability/drug effects , Chemical Phenomena , Chemistry, Physical , Filipin/pharmacology , Freeze Etching , Freeze Fracturing , Models, Biological , Structure-Activity RelationshipABSTRACT
This paper describes experiments showing the importance of the fatty acid chain length on the barrier properties of liposomal bilayers, prepared from saturated lecithins, under conditions of lateral phase separation. 1. Above the gel to liquid crystalline phase transition temperature, liposomes prepared from saturated lecithins with 14 or more carbon atoms per acyl chain exist as stable bilayers, which are practically impermeable to ions. 2. At temperatures well above the transition temperature dilauroyl phosphatidylcholine liposomes exhibited osmotic shrinkage, which was dependent on the ionic size of the solute used to bring about the osmotic gradient, indicating that the permeation through these less stable bilayers takes place mainly via individual diffusion of the permeating ions. 3. An enhanced release of trapped potassium from liposomes was demonstrated in the vicinity of the transition temperature. The extent of the increase, however, depended strongly on the length of the paraffin chain. 4. From measurements of the shrinkage behaviour of liposomes in the vicinity of the transition temperature it is concluded that the increased permeability decreases with increasing diameter of the permeating ion. This finding implies that the increased permeability at the transition temperature cannot be ascribed to "macroscopic" rupture of the liposomal membrane. The maximum permeability in the vicinity of the Tc is discussed in terms of probability and size distribution of statistical pore formation at the boundaries of liquid and solid domains.
Subject(s)
Fatty Acids , Liposomes , Phosphatidylcholines , Cations, Monovalent , Halogens , Osmolar Concentration , Osmosis , Permeability , Potassium , TemperatureABSTRACT
The osmotic behaviour of Acholeplasma laidlawii B cells was investigated with combined spectrophotometric and enzymatic measurements. The conclusion could be drawn that this osmotic behaviour depends largely on the physical state of the membrane lipids. When part of the membrane lipids is in the liquid-crystalline phase the cell is able to swell and behaves as a good osmometer. However, when the membrane lipid is in the gel phase, the cell is unable to swell and the change in absorbance of the cell suspension is then completely due to lysis.
