Ionophoretic activity

Assay of lonophore Activity. Ionophoretic activities on rat liver mitochondria and liposomes were performed as described previously (72). 

Ionophoretic Activity. PTX, even at high concentrations, had no ionophoretic activity on membranes of mitochondria and liposomes. 

Kitagawa I, Ohashi K, Kawanishi H, Shibuya H, Shinkai K, Akedo H (1989) Ionophoretic Activities of Oligopeptide Lactones and Resin-Glycosides in Human Erythrocytes. Chem Pharm Bull 37 1679... 

Isol. from tubers of Merremia mammosa. M. mammosa used as an Indonesian medicinal plant. Exhibits ionophoretic activity assists transport of alkali metal ions into human erythrocytes. Solid. 

There is a good deal of evidence that the therapeutic effects of antidepressants could involve adaptive changes in 5-HTia receptors. Postsynaptic 5-HTia receptor responses became implicated because the hyperpolarisation of hippocampal CA3 pyramidal neurons that follows ionophoretic administration of 5-HT was found to be increased after chronic treatment with most (but not all) antidepressants (Chaput, de Montigny and Blier 1991). Others suggested that antidepressants attenuate postsynaptic 5-HTja responses because the hypothermia, evoked by their activation, is diminished by antidepressants (Martin et al. 1992). 

The question of carrier design was first addressed for the transport of inorganic cations. In fact, selective alkali cation transport was one of the initial objectives of our work on cryptates [1.26a, 6.4]. Natural acyclic and macrocyclic ligands (such as monensin, valinomycin, enniatin, nonactin, etc.) were found early on to act as selective ion carriers, ionophores and have been extensively studied, in particular in view of their antibiotic properties [1.21, 6.5]. The discovery of the cation binding properties of crown ethers and of cryptates led to active investigations of the ionophoretic properties of these synthetic compounds [2.3c, 6.1,6.2,6.4-6.13], The first step resides in the ability of these substances to lipophilize cations by complexation and to extract them into an organic or membrane phase [6.14, 6.15]. 

Okadaic acid (OA), being a polyether, presents ionophoretic properties (facilitation of ion transport across membranes) as does CTX. It has been found that OA causes contraction in smooth muscles even in the absence of Ca (Ozaki and Karaki 1987 Shibata 1985). Ozaki and Karaki (1987) studied the mechanism of action of OA compared to calyculin A (another polyether isolated from a marine sponge). The results of this work suggest that OA has two separate effects activation of calcium channels as well as activating contractile elements to induce smooth muscle contraction. Recently, OA, in addition to other compounds from marine sources, has been found to be a tumor promoter that is, an agent that promotes tumor formation on already initiated cells (Fujiki 1988). It has been found that the OA class of tumor promoters bind to their own receptors which are present in particulate as well as cytosol fractions. The mechanism of action of these compounds has been partially elucidated. 

This compound is probably unique among the naturally occurring vitamin Bu-like compounds so far known in that it is active against pernicious anemia and for the chick (Bernhauer, 1955) and the flagellate Ochromonas malhamensis (Table II) (a microorganism which, as mentioned earlier, displays a specificity for vitamin Bw similar to that of birds and mammals (Ford, 1953)) as well as for E. coli and L. leichmannii. The chromatographic and ionophoretic properties illustrated in Fig. 1, with the other physical properties given by Friedrich and Bernhauer (1953), clearly differentiate Factor III from the cobalamins and from the other vitamin Bir-like factors. Its chemical relationship to these other compounds has not yet been established. 

Given 5-methylbenzimidazole and Factor B, E. coli synthesizes another new form of vitamin B12, active for E. coli, L. leichmannii, and Ochromonas (Ford, Holdsworth, and Kon, 1954). The compound appears chromatographically and ionophoretically homogeneous, but from theoretical considerations it might well prove to be a mixture of two compounds, one having 5-methyl and the other 6-methyl benzimidazole in the nucleotide. 

Figure 2. Schematic diagram the electrophysiological assay used to test for biological activity of spider venom components. Lx>ngitudinal ventrolateral muscles of Musca domestica were impaled with an intracellular microelectrode, which recorded excitatory junctional potentials (EJP) in response to nerve stimulation or ionophoretic junctional potentials (IP) in response to glutamate application by ionophoresis.

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