Paralytic activity of (des-Glu1)conotoxin GI analogs in the mouse diaphragm.

A series of 20 peptide analogs of (des-Glu1)conotoxin GI were prepared by solid phase synthesis. The peptides were tested for their abilities to inhibit contractions in the mouse-diaphragm-with-phrenic-nerve assay. (Des-Glu1)conotoxin has an IC50 of 2.7 x 10(-7) M in this assay. Results from this assay show that total loss of paralytic activity occurs when Pro is replaced by Gly, Tyr by D-Tyr, or Gly by D-Phe. In most cases loss or change in length of one of the disulfide rings eliminates paralytic activity except with compound 17, which is weakly active, IC50 = 7.0 x 10(-5) M. Replacement of the Cys1-Cys6 disulfide bond with an amide bond (compound 9) greatly lowers paralytic activity, IC50 = 3.7 x 10(-5) M.

Chelation of 238Pu(IV) in vivo by 3,4,3-LICAM(C): effects of ligand methylation and pH.

The linear tetracarboxycatecholate ligand, 3,4,3-LICAM(C) (N1,N5,N10,N14-tetrakis(2,3-dihydroxy-4-carboxybenzoyl-tetraaza tet radecane, tetra sodium salt) injected within 1 h after injection of Pu(IV) citrate, removes about the same fraction of Pu from animals as CaNa3-DTPA (diethylenetriaminepentaacetate, calcium, sodium salt) but removes less inhaled Pu than CaNa3-DTPA and leaves a Pu residue in the renal cortex. However, the formation constant of the expected Pu-3,4,3-LICAM(C) complexes are orders of magnitude greater than that of Pu-DTPA, and 3,4,3-LICAM(C) is 100 times more efficient than CaNa3-DTPA for removing Pu from transferrin in vitro. Because the formation constants of their actinide complexes are central to in vivo actinide chelation, ligand design strategies are dominated by the search for ligands with large Pu complex stabilities, and it was necessary to explain the failure of 3,4,3-LICAM(C) to achieve its thermodynamic potential in vivo. All the batches of 3,4,3-LICAM(C) prepared at Berkeley or in France [Euro-LICAM(C)] were found by high-pressure liquid chromatography to be mixtures of the pure ligand [55% in Berkeley preparations, 8.5% in Euro-LICAM(C)] and its four methylesters. A revised synthesis for 3,4,3-LICAM(C) is appended to this report. All of the incompletely hydrolyzed 3,4,3-LICAM(C) preparations and the pure ligand were tested for removal of Pu from mice [238Pu(IV) citrate intravenous, 30 mumol kg-1 of ligand at 1 h, kill at 24 h, radioanalyze tissues and separated excretal]. The presence of methylesters did not significantly impair the ability of the ligands to remove Pu from mice, and it did not alter the fraction of injected Pu deposited in kidneys. Temporary elevation (reduction) of plasma and urine pH of mice by 0.5 mL of 0.1 M NaHCO3 (NH4Cl) injected before or simultaneously with pure 3,4,3-LICAM(C) somewhat improved (significantly reduced) Pu excretion but had little influence on Pu deposition in kidneys. Review of the investigations of Pu removal from animals by 3,4,3-LICAM(C) revealed that the fractional renal Pu deposit was characteristic of the species and that it could be reduced by vigorous alkalinization which indicated the need to examine the details of the pH dependence of Pu complexation by 3,4,3-LICAM(C).(ABSTRACT TRUNCATED AT 400 WORDS)

Specific sequestering agents for the actinides: 10. Enhancement of 238Pu elimination from mice by poly(catechoylamide) ligands.

Macromolecules containing four sulfonated catecholy (2,3-dihydroxybenzoyl) groups are effective for decorporation of newly acquired Pu(IV). However, multiple injections in mice and single injections in dogs of 30 mumole/kg of 3,4,3-LICAM(S), the most effective sulfonated poly(catechoylamide) ligand, indicated that it would be toxic, so the ligand structure was modified. Each ligand was injected into mice (30 mumole/kg, intraperitoneally) 1 hr after an intravenous injection of 238Pu(IV) citrate, and mice were killed 24 hr after the Pu injection. Excreta and tissues were analyzed for Pu. (a) The number of catechoyl groups per molecule was reduced to suppress affinity for Fe(III). Net excretion (treated - control) of 55% of the injected Pu was promoted by tetrameric 3,4,3-LICAM(S), 51% by trimeric 3,4-LICAM(S), 22% by dimeric 2-LICAM(S), and 7.4% by the monomer, Tiron. (b) A mesitylene platform was substituted for the linear backbone. Net Pu excretion promoted by MECAM(S), a structurally less flexible trimer, was only 26%, and excretion was delayed. (c) A carboxyl substituent on the catechoyl groups reduced the acidity and hydrophilicity of the ligands. Tetrameric 3,4,3-LICAM(C) promoted 63% net Pu excretion, and one-third of that was fecal. The Pu contents of liver and skeleton were 33 and 44% of their respective 1-hr control values--compared to 51 and 44%, respectively, for CaNa3-DTPA. Mice given 30 mumole/kg of 3,4,3-LICAM(C) 20 times in 4 weeks showed no ill effects. (d) Large N-terminal alkane substituents added to 3,4,3-LICAM(C) increased ligand lipophilicity, hindered Pu chelation, and delayed excretion.

Tricatecholamide analogs of enterobactin as gallium- and indium-binding radiopharmaceuticals.

Isopropyl N-substituted tricatecholamide analogs of enterobactin have been found to form gallium and indium complexes with very high stability constants and to exhibit in vivo characteristics significantly different from gallium- or indium-transferrin and EDTA. The 3,4-DiP-LICAMS and TiP-MECAMS complexes were found to clear primarily through the kidneys, whereas the less polar 3,4-DiP-LICAM complex was eliminated through the liver. The rationale for developing new metal-binding analogs with larger organic groups attached to the amide nitrogens is discussed.

Synthetic enterobactin analogues. Carboxamido-2,3-dihydroxyterephthalate conjugates of spermine and spermidine.

Two examples of a new class of synthetic polycatecholate ligands, the carboxamido-2,3-dihydroxyterephthalate conjugates of spermine (8) and of spermidine (10), have been synthesized via the generally useful synthon methyl-2,3-dimethoxyterephthaloyl chloride (6). Initial biological evaluation reveals tetrameric terephthalate (8) to be an extremely effective agent for sequestering and removing plutonium from mice; a single 25-mumol/kg (ip) dose of 8 removed 73% of the plutonium citrate previously injected (iv, 1 h earlier). Under the same conditions, trimeric terephthalate (10) excreted only 49% of injected plutonium. In vitro kinetic experiments have shown that 10 rapidly and quantitatively removed Fe from human transferrin. These results are discussed in relation to the design of metal-ion specific sequestering agents.

Studies in the design of x-ray contrast agents. Synthesis, hydrophobicity, and solubility of some iodoresorcyl bis(beta-glucosides).

Two diiodo- and two triiodoresorcyl bis(beta-glucosides) were prepared and their hydrophobicity (log P octano) and water solubility were compared to a triiodophenyl beta-glucoside and several experimental nonionic, water-soluble, x-ray contrast agents. The data indicate steric overlap of the halogen substituents by the bulky hydrophilic O-beta-glucosyl substituents; high water solubility is attained only at observed log P octanol approximately 1.5 or lower. Of the new compounds, only 2,4,-6-triiodo-5-N-methylcarboxamidorescorcy bis(beta-glucoside) (6) was highly water soluble. At the physiological pHin dog's plasmia in vitro, compound 6 rapidly hydrolyzed. Poorly water-soluble but more stable compounds of this series were not appreciably absorbed from dog's duodenum.

Structure-activity relationships in luteinizing hormone-releasing hormone.

Three analogs of luteinizing hormone-releasing hormone (LH-RH) of the structure less than Glu-His-Trp-Ser-Tyr-Gly-Gly-Leu-Arg-Pro-Gly-NH2, involving substitutions inpositions 1, 3, and 8 with nonprotein amino acids, have been synthesized by the solid-phase method. They are [pyro-L-alpha-(1-aminoadipic)]-LH-RH, [3-(2-naphthyl)-L-Ala3]-LH-RH, and [delta-N-i-Pr-L-Orn8]-LH-RH. Their LH-RH activities in vivo were 12.5, 51.8, and 3.7% that of LH-RH, respectively, in the assay using ovariectomized, estrogen- and progesterone-treated rats. In a test based upon subcutaneous injection into immature male rats, [3-(2-naphthyl)-Ala3]-LH-RH released 1.2 times as much LH and 0.8 times as much FSH as synthetic LH-RH.

Synthesis of a potential water-soluble radiographic contrast medium, 2, 4, 6-triiodo-3-acetamido-5-N-methylcarboxamidophenyl beta-D-glucopyranoside.

Starting from 3,5-dinitrobenzoic acid, the infinitely water-soluble compound, 2, 4, 6-triiodo-3-acetamido-5-N-Methylcarboxamidophenyl Beta-D-glucopyranoside (9), was synthesized in nine steps. Glucoside 9, the first example of potentially a new class of water-soluble x-ray contrast media, is rapidly excreted from dog's plasma into the urine, unchanged. It has low intravenous toxicity in mice (LD50 = 24.5 g/kg). Thin-layer chromatography of aqueous solutions of 9 revealed first appearance of aglycon 7 after 1 week at room temperature.