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M Abramovitz

Publications and source records attributed to M Abramovitz.

At least 19 recordsLinked to original sources
PubMed2005

Effects of fibrates on human organic anion-transporting polypeptide 1B1-, multidrug resistance protein 2- and P-glycoprotein-mediated transport.

The effects of different fibric acid derivatives (bezafibrate, clofibrate, clofibric acid, fenofibrate, fenofibric acid and gemfibrozil) on human organic anion transporting-polypeptide 1B1 (OATP2, OATP-C, SLC21A6), multidrug resistance protein 2 (MRP2/ABCC2) and MDR1-type P-glycoprotein (P-gp/ABCB1) were examined in vitro. Cyclosporin A (a known inhibitor of OATP1B1 and P-gp), MK-571 (a known inhibitor of MRP2) and cimetidine (an organic cation) were also tested. Bezafibrate, fenofibrate, fenofibric acid and gemfibrozil showed concentration-dependent inhibition of estradiol 17-beta-D-glucuronide uptake by OATP1B1-stably transfected HEK cells, whereas clofibrate and clofibric acid did not show any significant effects up to 100 microM. Inhibition kinetics of gemfibrozil, which exhibited the most significant inhibition on OATP1B1, was shown to be competitive with a Ki = 12.5 microM. None of the fibrates showed any significant inhibition of MRP2-mediated transport, which was evaluated by measuring the uptake of ethacrynic acid glutathione into MRP2-expressing Sf9 membrane vesicles. Only fenofibrate showed moderate P-gp inhibition as assessed by measuring cellular accumulation of vinblastine in a P-gp overexpressing cell-line. Cyclosporin A significantly inhibited OATP1B1 and P-gp, whereas only moderate inhibition was observed on MRP2. The rank order of inhibitory potency of MK-571 was determined as OATP1B1 (IC50: 0.3 microM) > MRP2 (4 microM) > P-gp (25 microM). Cimetidine did not show any effects on these transporters. In conclusion, neither MRP2- nor P-gp-mediated transport is inhibited significantly by the fibrates tested. Considering the plasma protein binding and IC50 values for OATP1B1, only gemfibrozil appeared to have a potential to cause drug-drug interactions by inhibiting OATP1B1 at clinically relevant concentrations.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Molecular cloning and functional characterization of murine cysteinyl-leukotriene 1 (CysLT(1)) receptors.

We sought to clone and characterize the murine cysteinyl-leukotriene D(4) receptor (mCysLT(1)R) to complement our studies with leukotriene-deficient mice. A cDNA, cloned from trachea mRNA by reverse transcriptase-polymerase chain reaction, has two potential initiator ATG codons that would encode for polypeptides of 352 and 339 amino acids, respectively. These two potential forms, predicted to be seven transmembrane-spanning domain proteins, have 87% amino acid identity with the human CysLT(1) receptor (hCysLT(1)R). Membrane fractions of Cos-7 cells transiently expressing the short mCysLT(1)R demonstrated high affinity and specific binding for leukotriene D(4) (LTD(4), K(d) = 0.25 +/- 0.04 nM). In competition binding experiments, LTD(4) was the most potent competitor (K(i) = 0.8 +/- 0.2 nM) followed by LTE(4) and LTC(4) (K(i) = 86.6 +/- 24.5 and 100.1 +/- 17.1 nM, respectively) and LTB(4) (K(i) > 1.5 microM). Binding of LTD(4) was competitively inhibited by the specific CysLT(1) receptor antagonists MK-571 [(+)-3-(((3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl) ((3-(dimethylamino)-3-oxopropyl)thio)methyl)thio)propanoic acid], pranlukast (Onon), and zafirlukast (Accolate), while the CysLT(1)/CysLT(2) receptor antagonist BAY-u9773 [6(R)-(4'-carboxyphenylthio)-5(S)-hydroxy-7(E),9(E),11(Z),14(Z)-eicosatetrenoic acid] was 1000 times less potent than LTD(4). In transiently transfected HEK293-T cells expressing either the long or short form of mCysLT(1)R, LTD(4) induced an increase of intracellular calcium. In Xenopus laevis melanophores transiently expressing either isoform, LTD(4) induced the dispersion of pigment granules, consistent with the activation by LTD(4) of a G(alphaq) (calcium) pathway. Functional elucidation of mCysLT(1)R properties as described here will enable further experiments to clarify the selective role of LTD(4) in murine models of inflammation and asthma.

Aequorin↗
PubMed2001

Sequestration and phosphorylation of the prostaglandin E2 EP4 receptor: dependence on the C-terminal tail.

The prostaglandin E2 (PGE2) EP4 subtype is one of four prostanoid receptors that use PGE2 as the preferred ligand. We have investigated the agonist-mediated regulation of EP4 using a multifaceted approach. Short-term (30 min) agonist challenge of recombinant EP4 expressed in human embryonic kidney 293 cells (EP4-HEK293 cells) with PGE2 (1 microM) resulted in the desensitization of intracellular cyclic AMP (cAMP) accumulation and a reduction in cell surface [3H]PGE2 specific binding sites. These events correlated with sequestration of EP4, as visualized by immunofluorescence confocal microscopy and phosphorylation, as shown by [32P]orthophosphate labeling of the receptor. Stimulation of protein kinase A activity in EP4-HEK293 cells (10 microM forskolin or 1 mM 8-bromo-cAMP) did not induce EP4 desensitization, sequestration, or phosphorylation. In contrast, stimulation of protein kinase C activity (100 nM phorbol 12-myristate 13-acetate) attenuated PGE2-induced adenylyl cyclase activity and increased EP4 phosphorylation, but did not induce sequestration or a reduction in [3H]PGE2 specific binding sites. EP4 receptors containing a third intracellular loop deletion [EP4 (del. 215-263)] or a carboxyl-terminal tail truncation [EP4 (del. 355)] of EP4 were used to demonstrate that the C-terminal tail governs sequestration as well as phosphorylation of the receptor.

Amino Acid Sequence↗
PubMed2001

Expression of the prostaglandin E(2) (PGE(2)) receptor subtype EP(4) and its regulation by PGE(2) in osteoblastic cell lines and adult rat bone tissue.

Prostaglandins E (especially PGE(2)) stimulate bone formation and increase bone mass in several species including man. The mechanism for this effect, the target cells, and the receptors involved are not known. Specific cell-surface receptors for PGE(2) (EP(1-4)) have been cloned and characterized. EP(4) was reported to be the major receptor in embryonic and neonatal bone tissue in mice, especially in preosteoblasts; however, no data are available regarding its expression in adult bone. This study examines the expression of EP(4) in bone tissue of young adult rats, in which PGE(2) is markedly anabolic, and in various osteoblastic cell lines. Using northern blot analysis, we found that osteoblastic cell lines RCT-1, RCT-3, TRAB-11, and RP-1, primary osteoblastic cells harvested from fetal rat calvaria, as well as tibiae and calvariae of 5-week-old rats express 3.8 kb EP(4) messenger RNA (mRNA). Treatment of periosteal cells (RP-1) in vitro with 10(-6) mol/L PGE(2) increased the levels of both EP(4) mRNA and EP(4) protein, peaking at 1-2 h. Similarly, systemic administration of an anabolic dose of PGE(2) (3-6 mg/kg) to young adult rats upregulated the expression of EP(4) in the tibia and calvaria, also peaking at 1-2 h. Using in situ hybridization, we found increased expression of EP(4) in bone marrow cells of the tibial metaphysis in response to systemic PGE(2) treatment. The preosteoblastic nature of these EP(4)-expressing cells was suggested by the fact that dexamethasone-treated bone marrow stromal cells in culture express EP(4) mRNA, which is upregulated by PGE(2). Northern blot analysis failed to detect both basal and PGE(2)-induced EP(2) mRNA in the bone samples or cell lines tested. Taken together, these data implicate EP(4) as the major cyclic AMP-related PGE(2) receptor subtype expressed in bone tissue and osteoblastic cells and indicate that this receptor is upregulated by its ligand, PGE(2).

Animals↗
PubMed2001

Everyone is still on welfare: the role of redistribution in social policy.

Most people have an inaccurate assessment of who is "on welfare." Two decades have passed since Social Work published the original version of this article, which applied Titmuss's framework of a three-tiered social welfare system and showed that nearly "everyone is on welfare." Based on new data and a more in-depth analysis, this article re-examines who benefits from and who pays for social, fiscal, and corporate welfare and concludes that all three welfare systems continue to serve and to favor the middle class, wealthy households, and large corporations. Social workers can work to transform the system from one that rewards power and privilege to one that ensures distributive justice for all.

Health Care Rationing↗
PubMed2001

Key structural features of prostaglandin E(2) and prostanoid analogs involved in binding and activation of the human EP(1) prostanoid receptor.

The structure-activity relationship (SAR) of prostaglandin (PG) E(2) at the human EP(1) prostanoid receptor (designated hEP(1)) was examined via the binding and activation of this receptor by a series of 55 prostanoids and analogs. Using clonal human embryonic kidney 293 cell lines expressing recombinant hEP(1), affinity (K(i)), potency (EC(50)), and efficacy data were obtained using a radioligand competitive binding assay and an aequorin-based calcium functional assay. All compounds behaved as full agonists (90-100% of the response elicited by PGE(2)) in this assay, and the correlation between the K(i) and EC(50) values was highly significant (R(2) = 0.86). The results from the SAR analysis can be summarized as follows: 1) the existence and configuration of hydroxyl groups at the 11 and 15 positions of PGE(2) and prostanoid analog structures play a critical role in agonist activity; 2) the carboxyl group is also important for activity and modification of the carboxylic acid to various esters results in greatly reduced affinity and potency; 3) the activity of structures with moderate or weak potency can be enhanced by modification of the omega-tail; and 4) modifications to the ketone at the 9-position are better tolerated, with 9-deoxy-9-methylene-PGE(2) being the most potent agonist tested in the functional assay. The impact of other modifications on agonist potency is also discussed. The results from this study have identified, for the first time, the key structural features of PGE(2) and related prostanoids and prostanoid analogs necessary for activation of hEP(1).

Binding Sites↗
PubMed2000

Characterization of the human cysteinyl leukotriene 2 receptor.

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.

Adrenal Medulla↗
PubMed2000

A reporter gene assay for high-throughput screening of G-protein-coupled receptors stably or transiently expressed in HEK293 EBNA cells grown in suspension culture.

We describe in detail a robust, sensitive, and versatile functional assay for G-protein-coupled receptors (GPCRs) expressed in human embryonic kidney (HEK) 293-EBNA (Epstein-Barr virus nuclear antigen) (designated 293E) cells. The ability to grow these cells in suspension, in conjunction with the use of the secreted form of the human placental alkaline phosphatase (SEAP) as the reporter enzyme transcriptionally regulated by 5-cyclic AMP (cAMP) response elements (CREs) (Chen et al., Anal. Biochem. 226, 349-354 (1995)), makes this CRE-SEAP assay potentially attractive for high-throughput screening (HTS). A 293E clonal cell line, stably transfected with the CRE-SEAP plasmid, was initially characterized with compounds known to activate intracellular signal transduction pathways similar to those activated by GPCRs. Forskolin and cAMP analogues were potent at inducing SEAP expression but calcium ionophores (A23187 and ionomycin) were without effect. The forskolin response was also potentiated by the protein kinase C activator phorbol myristate acetate as well as the phosphodiesterase inhibitor isobutylmethylxanthine. Previously established cell lines expressing the G(alphas)-coupled DP or the G(alphaq)-coupled-EP(1) prostanoid receptors were stably transfected with the reporter gene construct and clones were selected based on their ability to secrete SEAP upon agonist challenge. Pharmacological characterization of the DP and EP(1) receptors displayed a similar rank order of potency for several known prostanoids and related compounds to that previously reported using classical binding assays or other functional assays. The CRE-SEAP assay was also used to characterize the EP(1) receptor antagonists SC-51322, SC-51089, and AH6809. In summary, we have established a reporter gene assay for GPCRs that couple to both G(alphas) and G(alphaq) and is amenable to HTS of both agonists and antagonists.

Base Sequence↗
PubMed2000

The utilization of recombinant prostanoid receptors to determine the affinities and selectivities of prostaglandins and related analogs.

Stable cell lines that individually express the eight known human prostanoid receptors (EP(1), EP(2), EP(3), EP(4), DP, FP, IP and TP) have been established using human embryonic kidney (HEK) 293(EBNA) cells. These recombinant cell lines have been employed in radioligand binding assays to determine the equilibrium inhibitor constants of known prostanoid receptor ligands at these eight receptors. This has allowed, for the first time, an assessment of the affinity and selectivity of several novel compounds at the individual human prostanoid receptors. This information should facilitate interpretation of pharmacological studies that employ these ligands as tools to study human tissues and cell lines and should, therefore, result in a greater understanding of prostanoid receptor biology.

Binding, Competitive↗
PubMed2000

Coexpression of full-length gamma-aminobutyric acid(B) (GABA(B)) receptors with truncated receptors and metabotropic glutamate receptor 4 supports the GABA(B) heterodimer as the functional receptor.

Direct evidence is lacking to show whether the gamma-aminobutyric acid (GABA)(B) gb1-gb2 heterodimer is the signaling form of the receptor. In this study, we tested whether gb1a or gb2 subunits when coexpressed with truncated receptors or metabotropic glutamate receptor mGluR4 could form functional GABA receptors. Coexpression of the ligand binding N-terminal domain of gb1a or the C-terminal portion of gb1a composing the seven-transmembrane segments and intracellular loops with gb2 could not reconstitute functional receptors. We next examined whether mGluR4, which forms homodimers and is structurally related to GABA(B), could act as a surrogate coreceptor for gb1 or gb2. The coexpression of mGluR4 and gb1a led to the expression of gb1a monomers on cell surface membranes as determined by immunoblot analysis and flow cytometry. However, mGluR4-gb1a heterodimers were not formed, and membrane-expressed gb1a monomers were not functionally coupled to adenylyl cyclase in human embryonic kidney 293 cells or activated inwardly rectifying potassium (Kir) channels in Xenopus oocytes. Similarly, the coexpression of mGluR4 and gb2 led to nonfunctional GABA receptors. GABA-activated distal signaling events resulted only after the coexpression and heterodimerization of gb1 and gb2. Taken together with the truncated receptor studies, the data suggest that a high degree of structural specificity is required to form the functional GABA(B) receptor that is a gb1-gb2 heterodimer.

Amino Acid Sequence↗
PubMed1999

Characterization of the cloned guinea pig leukotriene B4 receptor: comparison to its human orthologue.

A cDNA clone coding for the guinea pig leukotriene B4 (BLT) receptor has been isolated from a lung cDNA library. The guinea pig BLT receptor has an open reading frame corresponding to 348 amino acids and shares 73% and 70% identity with human and mouse BLT receptors, respectively. Scatchard analysis of membranes prepared from guinea pig and human BLT receptor-transfected human embryonic kidney (HEK) 293 EBNA (Epstein-Bar Virus Nuclear Antigen) cells showed that both receptors displayed high affinity for leukotriene B4 (Kd value of approximately 0.4 nM) and were expressed at high levels (Bmax values ranging from 9 to 12 pmol/mg protein). The rank order of potency for leukotrienes and related analogs in competition for [3H]leukotriene B4 specific binding at the recombinant guinea pig BLT receptor is leukotriene B4 > 20-OH-leukotriene B4 > 12(R)-HETE ((5Z,8Z,10E,12(R)14Z)-12-hydroxyeicosatetraen -1-oic acid) > 12(S)-HETE ((5Z,8Z,10E,12(S)14Z)-12-Hydroxyeicosatetraen -1-oic acid) > 20-COOH-leukotriene B4 > U75302 (6-(6-(3-hydroxy-1E,5Z-undecadienyl)-2-pyridinyl)-1,5-hexane diol) >> leukotriene C4 = leukotriene D4 = leukotriene E4. For the human receptor the rank order of 12(S)-HETE, 20-COOH-leukotriene B4 and U75302 was reversed. Xenopus melanophore and HEK aequorin-based reporter gene assays were used to demonstrate that the guinea pig and human BLT receptors can couple to both the cAMP inhibitory and intracellular Ca2+ mobilization signaling pathways. However, in the case of the aequorin-expressing HEK cells (designated AEQ17-293) transfected with either the guinea pig or human BLT receptor, expression of Galpha16 was required to achieve a robust Ca2+ driven response. Leukotriene B4 was a potent agonist in functional assays of both the guinea pig and human BLT receptors. U-75302 a leukotriene B4 analogue which possesses both agonistic and antagonistic properties behaved as a full agonist of the guinea pig and human BLT receptors in AEQ17-293 cells and not as an antagonist. The recombinant guinea pig BLT receptor will permit the comparison of the intrinsic potencies of leukotriene B4 receptor antagonists used in guinea pig in vivo models of allergic and inflammatory disorders.

Aequorin↗
PubMed1999

An automated aequorin luminescence-based functional calcium assay for G-protein-coupled receptors.

We describe in detail an automated and highly sensitive functional assay for calcium-coupled receptors (those receptors whose activation results in an increase in intracellular calcium levels) utilizing coelenterazine-charged aequorin as a probe for intracellular calcium levels ([Ca(2+)](i)). The assay was originally established to investigate Galpha(q)-coupled prostanoid receptors, which are members of the G-protein-coupled receptor (GPCR) superfamily, signaling through elevation of [Ca(2+)](i), initially focusing on the human EP(1) prostanoid receptor (hEP(1)). The parental human embryonic kidney cell line 293-AEQ17, developed by Button and Brownstein (Cell Calcium 14, 663-671, 1993), constitutively expresses apoaequorin and was used to develop a clonal cell line which stably coexpresses hEP(1). This cell line was used to optimize assay parameters in order to maximize accuracy and throughput in an automated 96-well format with the result that each 96-well plate can be completed in 70 min. Use of this flexible system will greatly simplify the functional analysis of GPCRs and other receptors which when activated result in increases in [Ca(2+)](i).

Aequorin↗
PubMed1999

Receptor for motilin identified in the human gastrointestinal system.

Motilin is a 22-amino acid peptide hormone expressed throughout the gastrointestinal (GI) tract of humans and other species. It affects gastric motility by stimulating interdigestive antrum and duodenal contractions. A heterotrimeric guanosine triphosphate-binding protein (G protein)-coupled receptor for motilin was isolated from human stomach, and its amino acid sequence was found to be 52 percent identical to the human receptor for growth hormone secretagogues. The macrolide antibiotic erythromycin also interacted with the cloned motilin receptor, providing a molecular basis for its effects on the human GI tract. The motilin receptor is expressed in enteric neurons of the human duodenum and colon. Development of motilin receptor agonists and antagonists may be useful in the treatment of multiple disorders of GI motility.

Alternative Splicing↗
PubMed1999

Characterization of the human cysteinyl leukotriene CysLT1 receptor.

The cysteinyl leukotrienes-leukotriene C4(LTC4), leukotriene D4(LTD4) and leukotriene E4(LTE4)-are important mediators of human bronchial asthma. Pharmacological studies have determined that cysteinyl leukotrienes activate at least two receptors, designated CysLT1 and CysLT2. The CysLT1-selective antagonists, such as montelukast (Singulair), zafirlukast (Accolate) and pranlukast (Onon), are important in the treatment of asthma. Previous biochemical characterization of CysLT1 antagonists and the CysLT1 receptor has been in membrane preparations from tissues enriched for this receptor. Here we report the molecular and pharmacological characterization of the cloned human CysLT1 receptor. We describe the functional activation (calcium mobilization) of this receptor by LTD4 and LTC4, and competition for radiolabelled LTD4 binding to this receptor by the cysteinyl leukotrienes and three structurally distinct classes of CysLT1-receptor antagonists. We detected CysLT1-receptor messenger RNA in spleen, peripheral blood leukocytes and lung. In normal human lung, expression of the CysLT1-receptor mRNA was confined to smooth muscle cells and tissue macrophages. Finally, we mapped the human CysLT1-receptor gene to the X chromosome.

Amino Acid Sequence↗
PubMed1999

Characterization of a novel serotonin receptor from Caenorhabditis elegans: cloning and expression of two splice variants.

Serotonin [5-hydroxytryptamine (5-HT)] modulates feeding activity, egg-laying, and mating behavior in the free-living nematode, Caenorhabditis elegans. We have cloned a novel receptor cDNA from C. elegans (5-HT2Ce) that has high sequence homology with 5-HT2 receptors from other species. When transiently expressed in COS-7 cells, 5-HT2Ce exhibited 5-HT binding activity and activated Ca2+-mediated signaling in a manner analogous to other 5-HT2 receptors. However, 5-HT2Ce displayed unusual pharmacological properties, which resembled both 5-HT2 and 5-HT1-like receptors but did not correlate well with any of the known 5-HT2 subtypes. Two splice variants of 5-HT2Ce that differ by 48 N-terminal amino acids were identified. The two isoforms were found to have virtually identical binding and signaling properties but differed in their levels of mRNA expression, with the longer variant being four times more abundant than the shorter species in all developmental stages tested. Taken together, the results describe two variants of a novel C. elegans 5-HT receptor, which has some of the properties of the 5-HT2 family but whose pharmacological profile does not conform to any known class of receptor.

Aequorin↗
PubMed1998

Nuclear localization of prostaglandin E2 receptors.

Prostaglandin E2 receptors (EP) were detected by radioligand binding in nuclear fractions isolated from porcine brain and myometrium. Intracellular localization by immunocytofluorescence revealed perinuclear localization of EPs in porcine cerebral microvascular endothelial cells. Nuclear association of EP1 was also found in fibroblast Swiss 3T3 cells stably overexpressing EP1 and in human embryonic kidney 293 (Epstein-Barr virus-encoded nuclear antigen) cells expressing EP1 fused to green fluorescent protein. High-resolution immunostaining of EP1 revealed their presence in the nuclear envelope of isolated (cultured) endothelial cells and in situ in brain (cortex) endothelial cells and neurons. Stimulation of these nuclear receptors modulate nuclear calcium and gene transcription.

3T3 Cells↗
PubMed1998

Characterization of the recombinant human prostanoid DP receptor and identification of L-644,698, a novel selective DP agonist.

1. A human embryonic kidney cell line [HEK 293(EBNA)] stably expressing the human recombinant prostaglandin D2 (PGD2) receptor (hDP) has been characterized with respect to radioligand binding and signal transduction properties by use of prostanoids and prostanoid analogues. Radioligand binding studies included saturation analyses, the effects of nucleotide analogues, the initial rate of ligand-receptor association and equilibrium competition assays. In addition, adenosine 3':5'-cyclic monophosphate (cyclic AMP) generation in response to ligand challenge was also measured, as this is the predominant hDP signalling pathway. 2. L-644,698 ((4-(3-(3-(3-hydroxyoctyl)-4-oxo-2-thiazolidinyl) propyl) benzoic acid) (racemate)) was identified as a novel ligand having high affinity for hDP with an inhibitor constant (Ki) of 0.9 nM. This Ki value was comparable to the Ki values obtained in this study for ligands that have previously shown high affinity for DP: PGD2 (0.6 nM), ZK 110841 (0.3 nM), BW245C (0.4 nM), and BW A868C (2.3 nM). 3. L-644,698 was found to be a full agonist with an EC50 value of 0.5 nM in generating cyclic AMP following activation of hDP. L-644,698 is, therefore, comparable to those agonists with known efficacy at the DP receptor (EC50): PGD2 (0.5 nM), ZK 110841 (0.2 nM) and BW245C (0.3 nM). 4. L-644,698 displayed a high degree of selectivity for hDP when compared to the family of cloned human prostanoid receptors: EP1 (> 25,400 fold), EP2 (approximately 300 fold), EP3-III (approximately 4100 fold), EP4 (approximately 10000 fold), FP (> 25,400 fold), IP (> 25,400 fold) and TP (> 25,400 fold). L-644,698 is, therefore, one of the most selective DP agonists as yet described. 5. PGJ2 and delta12-PGJ2, two endogenous metabolites of PGD2, were also tested in this system and shown to be effective agonists with Ki and EC50 values in the nanomolar range for both compounds. In particular, PGJ2 was equipotent to known DP specific agonists with a Ki value of 0.9 nM and an EC50 value of 1.2 nM.

Adenine Nucleotides↗