Isokotanins A-C: new bicoumarins from the sclerotia of Aspergillus alliaceus

Three new bicoumarin metabolites, isokotanins A [1], B [2], and C [3], were isolated from the sclerotia of Aspergillus alliaceus. Isokotanin A is a regioisomer of the known bicoumarin kotanin [4]. The structures and spectral assignments for 1-3 were determined on the basis of selective INEPT, HMQC, and NOESY nmr data, as well as by chemical interconversions. Isokotanins B and C show activity against the corn earworm Helicoverpa zea and the dried fruit bettle Carpophilus hemipterus. The known compounds kotanin [4], desmethylkotanin [5], nominine, and paspaline were also isolated from extracts of A. alliaceus sclerotia.     

Prevalence of vitamin D insufficiency in an adult normal population

Demethylation of some aconitine-type norditerpenoid alkaloids was carried out with trimethylsilyl iodide and with HBr in glacial AcOH. Aconitine (10), cammaconine (23), delphinine (3), falconerine (18), lappaconitine (22), and talatizamine (24) afforded partially demethylated products. When methoxyl groups are present at the C-16 and C-18 positions, these are demethylated, and the methoxyl group at the C-1 position underwent demethylation in none the alkaloids studied except falconerine (18). With HBr-AcOH, in the case of alkaloids possessing a C-3 hydroxyl group, the methoxymethyl at C-18 formed a tetrahydrofuran, cyclizing at the C-6 position. Detailed NMR spectral studies (1H, 13C, 1H homonuclear COSY, HETCOR, and selective INEPT) carried out on the demethylation products have enabled accurate chemical shift assignments to be made for the demethylated alkaloids.     

Triterpenoid saponins from Gypsophila oldhamiana

Three new triterpenoid saponins were isolated from the roots of Gypsophila oldhamiana. Their structures were elucidated, using a combination of homonuclear and heteronuclear 2D nmr and fabms, as 3-0-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranolyl-(1-->3)] -beta-D-glucuronopyranosyl quillaic acid methyl ester [1], 3-0-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta- D-glucuronopyranosyl gypsogenin methyl ester [2], and 3-0-beta-D-galactopyranolsyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3) ]-beta-D-glucuronopyranosyl quillaic acid 28-[0-beta-D-fucopyranosyl(1-->4)-beta-D-glucopyranosyl(1-->3)]-alpha-L- rhamnopyranosyl] ester.     

Celahinine A, a new sesquiterpene pyridine alkaloid from Celastrus hindsii

A new sesquiterpene pyridine alkaloid, celahinine A [1], and the related known polyester celahin A, as well as the known cytotoxic sesquiterpene pyridine alkaloid emarginatine A [2], were isolated from Celastrus hindsii. The structure of 1 was determined by 2D nmr techniques and was also confirmed by spectral comparison with the related 2.     

Triterpenoid saponins from Vaccaria segetalis

Four novel triterpenoid saponins were isolated from the seeds of Vaccaria segetalis. Their structures were established as vaccaroside A, gypsogenic acid-28-O-beta-D- glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->6)-[beta-D- glucopyranosyl-(1-->3)]-beta-D-glucopyranoside; vaccaroside B, gypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->2)-[3-hydroxyl-3- methylglutaroyl-(1-->6)]-beta-D-glucopyranosyl-(1-->6)-[beta-D- glucopyranosyl-(1-->3)]-beta-D-glucopyranoside; vaccaroside C, 23-O-beta-D-glucopyranosyl-gypsogenic acid-28-O-beta-D- glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->6)- [beta-D-glucopyranosyl-(1-->3)]-beta-D-glucopyranoside and vaccaroside D, 3,4-secogypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->3)- [beta-D-glucopyranosyl-(1-->6)]-beta-D-glucopyranoside by a combination of extensive NMR (DEPT, COSY, HOHAHA, HETCOR, HMBC and NOESY) studies and chemical degradation.     

Left ventricular dysfunction after open repair of simple congenital heart defects

A new triterpenoid saponin, coumoside A, has been isolated from the whole plant of Cyclamen coum and the structure of this novel saponin (C58H92O27) has been deduced by NMR methods based on 1H, 13C, DEPT, 1H-1H COSY, HETCOR, NOESY-NMR experiments and the FAB-mass spectrum. It has the structure 3 beta-O-[beta-D-glucopyranosyl-(1-6)-[alpha-L-arabinopyranosyl- (1-2)]-beta-D-glucopyranosyl-(1-4)-[beta-D-glucopyranosyl-(1-2)]-alpha-L -arabinopyranosyl]-16 alpha-hydroxy-30,28 beta-lactone-olean-12-ene and is called coumoside.     

Effect of variability of plasma interferences on the accuracy of drug immunoassays

Three bond proton-proton vicinal coupling constants are of potential value for analyzing sugar conformations in DNA. However, self-cancellation in antiphase cross peaks and modulation of peak splittings by transverse cross relaxation can alter the apparent coupling constants such that they do not accurately reflect the sugar conformations. Transverse cross relaxation is most effective between strongly coupled geminal proton pairs. Here we report the use of stereospecific deuteration at the H2" position in the A5 and A6 residues in the 12 base pair DNA sequence [d(CGCGAATTCGCG)2] as a means of investigating the effect of transverse cross relaxation on P.E.COSY type cross peaks. Deuteration of the H2" proton is expected to reduce the transverse cross relaxation rate by the square of ratio of the proton to deuteron gyromagnetic ratios, i.e., by a factor of 42. Additionally, a striking eight- to ninefold increase in the signal intensity was observed for cross peaks involving the remaining H2' proton resulting from diminished dipolar relaxation. Further improvements in signal-to-noise ratio were realized by collecting P.E.COSY spectra in strips, using an experiment referred to as stripe-COSY, employing selective excitation pulses which reduced the number of required t1 increments by a factor of four. A final improvement was achieved by employing selective time-shared homonuclear decoupling during the acquisition period, in an experiment referred to as superstripe-COSY, to collapse splittings due to passive couplings. Collectively, these approaches provide P.E. COSY-type spectra with two to three orders of magnitude increased sensitivity per unit time and that are relatively free from artifacts.     

Metabolism of daidzein and genistein by intestinal bacteria

The isoflavones daidzein [1] and genistein [2] were fermented with human fecal bacteria under anaerobic conditions. Dihydrodaidzein [3], benzopyran-4,7-diol,3-(4-hydroxyphenyl) [4], and equol [5] were isolated from the fermentation broth of 1. Only one metabolite, dihydrogenistein [6], was isolated and characterized from the fermentation broth of 2. Metabolites 3-6 were identified by spectral methods.     

Structure of an acidic exopolysaccharide of Burkholderia pseudomallei

A recently described water-soluble exopolysaccharide of Burkholderia pseudomallei recognized by the IgG 1 monoclonal antibody 3015 [Steinmetz, I., Rohde, M. & Brenneke, B. (1995) Infect. Immun. 63, 3959-3965] was isolated by repetitive ethanol-precipitation steps and by anion-exchange chromatography. The structure of the polysaccharide was determined by a combination of chemical-derivatization and mass-spectrometric techniques (compositional and methylation analysis, GC/MS, and electrospray-ionization-MS/MS of reduced and permethylated hydrolytic fragments), and two-dimensional 1H-NMR methods (COSY, TOCSY and NOESY) and confirmed by isolation and structural characterization of the depolymerized repeating unit of the polysaccharide. The combined structural data established a linear tetrasaccharide repeating unit consisting of three galactose residues, one bearing a 2-linked O-acetyl group, and a 3-deoxy-D-manno-2-octulosonic acid residue. [-->3)-beta-D-Galp2Ac-(1-->4)-alpha-D-Galp-(1-->3)-beta-D-Galp-(1- ->5)-beta-Kdo-(2-->]n     

Structural analogues of cumambrin B from the flower of Chrysanthemum boreale

The structural analogues of cumambrin B (1, 2, 3, 4) were isolated from the flower of Chrysanthemum boreale Makino. The structures of compounds were determined by two-dimensional 1H-1H COSY and 13C-1H COSY spectra with the aid of homonuclear and heteronuclear double resonance experiment. The stereochemistry of compounds has been verified from single crystal X-ray diffraction of cumambrin A (2). The antimicrobial activities of these guaianolides have been studied.     

Structural studies by high-field NMR spectroscopy of a binary-addressed complementary oligonucleotide system juxtaposing pyrene and perfluoro-azide units

Recently, a new approach has been proposed to improve the site-specificity and efficiency of the modification of nucleic acid target sequences, the binary system of complementary-addressing nucleic acid sequences. The binary system comprises two oligonucleotides, one modified with a photosensitizing group and the other with a photoreactive group. The sites of chemical modification are arranged to bring the two chemical functions close enough together in space to allow efficient energy transfer from the photo-excited photosensitizer to an arylazide moiety which expels N2 to form a nitrene which subsequently covalently labels the target nucleic acid. Structural analysis performed by high-resolution 2D NMR spectroscopy (400 MHz and 600 MHz) are reported for the model binary system 1:2:3, where 1 is the target 12-mer pdGTATCAGTTTCT, 2 is a photoactivatable fluoroazide derivative dAGAAACp-L-Az and 3 is the photosensitizer derivative Pyr-pdTGATAC (here: Az is the p-azidotetrafluorobenzyl group, Pyr the pyrenyl-1-methylamino group, L a linker group). The assignment of oligonucleotide and modifying group protons was performed using 1H COSY, TOCSY and NOESY experiments. Comprehensive analysis of 1H NOESY spectra of 1:2:3 showed that terminal fragments of the complex [5'p-1T-2G-3A-4T-], [-21A-22T-23A-24C], [-8T-9T-10T-11C-12T] and [13A-14G-15A-15A-17A-18C-] gave a continuous set of intra- and inter-nucleotide interactions, typical of regular double-stranded B-DNA. In contrast, the central region of the complex composed of 5C, 6A, 7G, 19T and 20G nucleotide residues, nearest the Pyr and Az groups, was found to be distorted. Thus some signals from aromatic and/or sugar-ring protons of the above nucleotide residues were extremely broadened or almost absent. Moreover, some intra- and/or inter-nucleotide interactions, typical of the regular DNA duplex, were not detected for the [-5C-6A-7G-] and [-19T-20G-] regions of the tandem system. Instead of that, some cross-peaks of low-intensity between the H2 proton of the Pyr group and 7G(H1'), 7G(H2'/H2"), 7G(H3'), 4T(H2"), 4T(H4') and 4T(H5'/H5") were observed. Additional 1H -1H NOE-interactions between methylene protons of the linker group L and some sugar ring protons of 18C nucleotide residue were detected. A preliminary structural model, constructed using proton-proton distances between Pyr and the DNA and Az-L and DNA obtained from a 1H NOESY experiment at 300 ms mixing time as constraints for the refinement of the structure, displayed significant distortion from B-DNA of the double-stranded helix in the middle of the complex, (-5C-6A-7G, -18C-19T-20G-). The Pyr group was located in what remains of the minor groove near 4T, 5C, 6A and 7G and the centroid of the azide ring less than 9A degrees from the centroid of the ring system of Pyr group.     

Structure of a neutral O-specific polysaccharide of the bacterium Proteus mirabilis O24

Lipopolysaccharide of the bacterium Proteus mirabilis O24 was found to have a neutral O-specific polysaccharide chain containing D-galactose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose in ratios 1:2:1. On the basis of 1H- and 13C-NMR spectroscopy, including two-dimensional correlation spectroscopy (COSY), H-detected 1H, 13C heteronuclear multiple-quantum coherence (HMQC), and nuclear Overhauser effect spectroscopy (NOESY), the following structure of the branched tetrasaccharide repeating unit of the O-specific polysaccharide was established: -->3)-beta-D-GlcpNAc-(1-->4)-beta-D-GalpNAc-(1-->4)-beta-D-GlcpNAc-(1--> [formula: see text] beta-D-Galp.     

Management of chronic myeloid leukaemia

A tetrasaccharide related to the blood group oligosaccharides, known as sialyl LewisX, has been proposed as the receptor for the lectin responsible for leukocyte adhesion named alternatively as E-selectin or ELAM-1. The 13C- and 1H-nmr spectra have been completely assigned for a tetrasaccharide model of this receptor, Neu5Ac alpha-(2-->3)-Gal beta-(1-->4)-[Fuc alpha-(1-->3)-]GlcNAc beta-NHAc. Quantitative nuclear Overhauser data (NOESY) have been recorded and analyzed by a complete spin matrix simulation method. Conformational space was exhaustively searched and all conformational models whose simulated NOESY spectra matched the experiment were found. Molecular mechanics and molecular dynamics calculations were carried out to test whether the experimental conformations are low energy and thus likely to represent true single conformations for the tetrasaccharide. It was concluded that while the LewisX trisaccharide portion of the compound adopts a single conformation, there is likely to be some flexibility about the Neu5Ac alpha-(2-->3)-linkage. A model featuring fast exchange between two different conformations of this linkage is found to be consistent with both the nmr experiments and the molecular dynamics simulations.     

NMR spectroscopic elucidation of the structure of a glycerol teichoic acid-like O-specific polysaccharide of the bacterium Hafnia alvei strain PCM 1199

The structure of the acidic O-specific polysaccharide of a Gram-negative bacterium, H. alvei strain PCM 1199, was studied by NMR spectroscopy including two-dimensional correlation spectroscopy (COSY), total correlation spectroscopy (TOCSY), nuclear Overhauser effect spectroscopy (NOESY), 1H, 13C heteronuclear single-quantum coherence (HSQC), 1H, 13C heteronuclear multiple-bond correlation (HMBC), and one-dimensional 1H, 31P heteronuclear multiple-quantum coherence (HMQC) experiments. It was found that the polysaccharide contains D-galactose, 2-acetamido-2-deoxy-D-glucose, 4-acetamido-4,6-dideoxy-D-glucose, glycerol, and phosphate in the ratios 1:2:1:1:1, as well as O-acetyl groups in non-stoichiometric amounts. The polysaccharide is similar in structure to teichoic acids of Gram-positive bacteria and has the following structure of the repeating unit: 3)-beta-D-Galp-(1-->3)-alpha-D-GlcpNAc-(1-->3)-beta-D-Quip4NAc-(1- ->1)-Gro- 3-P-(O--> [formula: see text] beta-D-GlcpNAc [formula: see text] The O-specific polysaccharide of H. alvei PCM 1199 is structurally related to another teichoic acid-like O-specific polysaccharide of H. alvei PCM 1205 studied by us earlier.     

Simultaneous quantification of serotonin, dopamine and noradrenaline levels in single frontal cortex dialysates of freely-moving rats reveals a complex pattern of reciprocal auto- and heteroreceptor-mediated control of release

In the present study, a novel and exceptionally sensitive method of high-performance liquid chromatography coupled to coulometric detection, together with concentric dialysis probes, was exploited for an examination of the role of autoreceptors and heteroceptors in the modulation of dopamine, noradrenaline and serotonin levels in single samples of the frontal cortex of freely-moving rats. The selective D3/D2 receptor agonist, CGS 15855A [(+/-)-trans-1,3,4,4a,5,10b-hexahydro-4-propyl-2H-[1]benzopyrano[3 ,4-b]-pyridin-9-ol], and antagonist, raclopride, respectively decreased (-50%) and increased (+60%) levels of dopamine without significantly modifying those of serotonin and noradrenaline. The selective alpha2-adrenergic receptor agonist, dexmedetomidine, markedly decreased noradrenaline levels (-100%) and likewise suppressed those of serotonin and dopamine by -55 and -45%, respectively. This effect was mimicked by the preferential alpha2-adrenergic receptor agonist, guanabenz (-100%, -60% and -50%). Furthermore, the alpha2-adrenergic receptor antagonist, RX 821,002 [2(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline], and the preferential alpha2A-adrenergic receptor antagonist, BRL 44408 [2-(2H-(1-methyl-1,3-dihydroisoindole)methyl)-4,5-dihydroimidaz ole], both evoked a pronounced elevation in levels of noradrenaline (+212%, +109%) and dopamine (+73%, +85%). In contrast, the preferential alpha(2B/2C)-adrenergic receptor antagonist, prazosin, did not modify noradrenaline and dopamine levels. RX 821,002 and BRL 44408 did not significantly modify levels of serotonin, whereas prazosin decreased these levels markedly (-55%), likely due to its alpha1-adrenergic receptor antagonist properties. The selective serotonin-1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), reduced serotonin levels (-65%) and increased those of dopamine and noradrenaline by +100%), and +175%, respectively. The selective serotonin-1A antagonist, WAY 100,635 [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclo- hexanecarboxamide], which had little affect on monoamine levels alone, abolished the influence of 8-OH-DPAT upon serotonin and dopamine levels and significantly attenuated its influence upon noradrenaline levels. Finally, the selective serotonin-1B agonist, GR 46611 [3-[3-(2-dimethylaminoethyl)-1H-indol-5-yl]-N-(4-methoxybenzyl)acrylamid e], decreased serotonin levels (-49%) and the serotonin-1B antagonist, GR 127,935 [N-[4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-2'-methyl-4'-(5-me thyl-1,2,4-oxadiazol-3-yl)-biphenyl-4-carboxamide], which did not significantly modify serotonin levels alone, abolished this action of GR 46611. Levels of dopamine and noradrenaline were not affected by GR 46611 or GR 127,935. In conclusion, there is a complex pattern of reciprocal autoreceptor and heteroceptor control of monoamine release in the frontal cortex. Most notably, activation of alpha2-adrenergic receptors inhibits the release of noradrenaline, dopamine and serotonin in each case, while stimulation of serotonin-1A receptors suppresses serotonin, yet facilitates noradrenaline and dopamine release. In addition, dopamine D2/D3 autoreceptors restrain dopamine release while (terminal-localized) serotonin-1B receptors reduce serotonin release. Control of serotonin release is expressed phasically and that of noradrenaline and dopamine release tonically.     

Structure of the O-specific polysaccharide of Citrobacter freundii O3a,3b,1c

The following structure of the O-specific polysaccharide of Citrobacter freundii O3a,3b,1c containing D-mannose and D-rhamnose was established using sugar analysis and NMR spectroscopy, including computer-assisted analysis of the 13C NMR spectrum, 2D COSY, H,H-relayed COSY, heteronuclear 13C, 1H correlation (HETCOR), and rotating-frame NOE spectroscopy (ROESY):-->4)-alpha-D-Manp-(1-->3)-beta-D-Rhap-(1-->4) -beta-D-Rhap-(1-->.     

Diagnostic value of otoacoustic emissions. 1

Analogues of the potent and selective 5-HT1A ligand, WAY 100635, were synthesized and examined as potential candidates for imaging 5-HT1A receptors by positron emission tomography (PET). Several of the analogues displayed nanomolar affinity for the 5-HT1A receptor, comparable to WAY 100635. Three of these were examined in a model of human liver metabolism vis-à-vis WAY 100635. All showed a markedly lower propensity for amide hydrolysis than WAY 100635. Radiolabelling of these three potential PET radiotracers with carbon-11 was readily achieved from [11C]-iodomethane, and the newly synthesized radioligands were tested in vivo in rats for binding to 5-HT1A receptors. Whereas two of the ligands failed to bind to 5-HT1A receptors in vivo, one was successful. The latter, [11C]-7 [4-(2'-methoxyphenyl)-1-[2'-[N-(2'-pyridinyl)-2-bicyclo[2.2.2]octanec arboxamido]ethyl]-piperazine], showed good brain penetration, hippocampal:cerebellar ratios of 10:1 at 45 min postinjection. Blocking studies with a variety of drugs demonstrated that the binding of [11C]-7 in vivo was selective for 5-HT1A receptors. [11C]-7 is a promising candidate as a ligand for imaging 5-HT1A receptors by PET.     

Assigning the NMR spectra of aromatic amino acids in proteins: analysis of two Ets pointed domains

The measurement of interproton nuclear Overhauser enhancements (NOEs) and dihedral angle restraints of aromatic amino acids is a critical step towards determining the structure of a protein. The complete assignment of the resonances from aromatic rings and the subsequent resolution and identification of their associated NOEs, however, can be a difficult task. Shown here is a strategy for assigning the 1H, 13C, and 15N signals from the aromatic side chains of histidine, tryptophan, tyrosine, and phenylalanine using a suite of homo- and hetero-nuclear scalar and NOE correlation experiments, as well as selective deuterium isotope labelling. In addition, a comparison of NOE information obtained from homonuclear NOE spectroscopy (NOESY) and 13C-edited NOESY-heteronuclear single quantum correlation experiments indicates that high-resolution homonuclear two-dimensional NOESY spectra of selectively deuterated proteins are invaluable for obtaining distance restraints to the aromatic residues.     

Further lupane lactones from Kokoona ochracea

Additional new lupane lactones were isolated from the stem bark of Kokoona ochracea (Celastraceae). Their structures have been elucidated, through the application of 1D and 2D nmr spectroscopic methods, as 20,29-dihydroxy-3-oxolupan-30,21 alpha-olide (ochraceolide D) [1] and 28-hydroxy-3-oxolup-20(29)-en-30,21 alpha-olide (ochraceolide E) [2]. These compounds and the mono- and di-acetates of ochraceolide D (4 and 5, respectively) were evaluated for in vitro cytotoxic activity against P-388 murine lymphocytic leukemia cells and a panel of human cancer cell systems. Ochraceolide D [1] was significantly cytotoxic (ED50, 3.9 micrograms/ml) against human glioblastoma (U373) cells. Other compounds (4, 5, and 2) exhibited only a weak cytotoxic response in certain cancer cell lines.     

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate in rats and mice

8-epi-prostaglandin F2 alpha stimulated contraction of human myometrial strips obtained from five different donors at the time of hysterectomy with a pEC50 value of 6.3 +/- 0.5. In paired strips from the same donors the pEC50 value for the selective TP receptor agonist U46619 ([1R-[1a,4a,5b(Z),6a(1E,3S*)]]-7-[6-(3- hydroxy-1-octenyl)-2-oxabicyclo[2.2.1]hept-5-yl]-5-heptenoic acid) was 8.3 +/- 0.4. In strips from four other donors 8-epi-prostaglandin F2 alpha was ineffective whereas the pEC50 for U46619 was 6.9 +/- 0.3. Responses to 8-epi-prostaglandin F2 alpha were unaffected by the selective DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2- cyclohexyl-2-hydroxyethylamino)hydantoin) at 50 nM but were blocked by the selective TP receptor antagonist L670596 ((-)6,8-difluoro-9-p-methylsulfonyl benzyl-1,2,3,4- tetrahydrocarbazol-1-yl-acetic acid) at 50 nM. The pIC50 values obtained when the TP receptor antagonists GR 32191 ([1R- [1 alpha(Z),2 beta,3 beta,5 alpha]]-(+)-7-[5-[[(1,1'-biphenyl)-4- yl]methoxy]-3-hydroxy-2-(1-piperidinyl)cyclopentyl]-4-heptenoic acid), ICI D1542 ((4(Z)-6-[(2S,4S,5R)-2-[1-methyl-1-(2-nitro-4-tolyloxy)ethyl]- 4-(3-pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid), ICI 192605 (4(Z)-6-[(2,4,5-cis)-2-(2-chlorophenyl)-4-(2-hydroxyphenyl)-1,3- dioxan-5-yl]hexenoic acid), L670596 and SQ 29548 ([1S-(1 alpha,2 beta(5Z),3 beta,4 alpha]]-7- [3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7- oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid) were added cumulatively to strips pre-contracted with an EC80 concentration of 8-epi-prostaglandin F2 alpha were not significantly different from those obtained when an EC80 concentration of U46619 was used. The effects of 8-epi-prostaglandin F2 alpha on strips pre-contracted with an EC80 concentration of U46619 were not different from those of U46619 itself. It is concluded that in the non-pregnant human myometrium 8-epi-prostaglandin F2 alpha is a medium potency contractile agonist acting predominantly at the TP receptor.