sq-29548 and carboprostacyclin

The pharmacological properties of [(3)H]-prostaglandin E(2) ([(3)H]-PGE(2)) binding to washed homogenates of hamster uterus were determined. Scatchard analysis of competition data yielded dissociation constants (K(d)s) of 30.9 +/- 5.6 nM (n = 3) and apparent receptor density (B(max)) of 25.25 +/- 1.89 pmol g(-1) wet weight tissue (74 +/- 8% specific binding). Competition studies yielded the following affinity parameters (K(i)) for various prostanoids: GR63799X = 13 4 nM; PGE(2) = 17 +/- 3 nM; sulprostone = 64 +/- 5 nM; enprostil = 67 +/- 3 nM; misoprostol = 124 +/- 15 nM; cloprostenol = 187 +/- 33 nM; carba-prostacyclin = 260 +/- 167 nM; iloprost = 555 +/- 162 nM; PGF(2 alpha) = 767 +/- 73 nM; PGD(2) > 3560 nM; fluprostenol = 11 790 +/- 2776 nM; RS93520 = 21 558 +/- 14 228 nM. These data closely matched the pharmacological profile of previously described EP(3) receptors such as in bovine corpus luteum (BCLM) and the cloned mammalian EP(3) receptors. The high correlation between the current hamster uterus pharmacology data vs the EP(3) receptor binding in BCLM (r = 0.94; P < 0.0001), vs cloned human EP(3) receptor (r = 0.94, P < 0.0001), vs the cloned mouse EP(3) receptor binding (r = 0.78; P < 0.002), vs cloned rat EP(3) receptor (r = 0.9, P < 0.0004), and vs EP(3) receptor-mediated functional responses (r = 0.72, P < 0.02) substantiated the conclusion that the hamster uterus contains EP(3) receptor binding sites.

Topics: Animals; Binding Sites; Biphenyl Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cattle; Cloprostenol; Cricetinae; Dinoprost; Dinoprostone; Enprostil; Epoprostenol; Fatty Acids, Unsaturated; Female; Hydantoins; Hydrazines; Iloprost; Latanoprost; Misoprostol; Prostaglandins; Prostaglandins E, Synthetic; Prostaglandins F, Synthetic; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP3 Subtype; Tritium; Uterus

Prostaglandin endoperoxide H synthases and their arachidonate products have been implicated in modulating angiogenesis during tumor growth and chronic inflammation. Here we report the involvement of thromboxane A(2), a downstream metabolite of prostaglandin H synthase, in angiogenesis. A TXA(2) mimetic, U46619, stimulated endothelial cell migration. Angiogenic basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) increased TXA(2) synthesis in endothelial cells three- to fivefold. Inhibition of TXA(2) synthesis with furegrelate or CI reduced HUVEC migration stimulated by VEGF or bFGF. A TXA(2) receptor antagonist, SQ29,548, inhibited VEGF- or bFGF-stimulated endothelial cell migration. In vivo, CI inhibited bFGF-induced angiogenesis. Finally, development of lung metastasis in C57Bl/6J mice intravenously injected with Lewis lung carcinoma or B16a cells was significantly inhibited by thromboxane synthase inhibitors, CI or furegrelate sodium. Our data demonstrate the involvement of TXA(2) in angiogenesis and development of tumor metastasis.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Benzofurans; Bridged Bicyclo Compounds, Heterocyclic; Chemotaxis; Dinoprost; Dinoprostone; Endothelial Growth Factors; Endothelium, Vascular; Enzyme Inhibitors; Epoprostenol; Fatty Acids, Unsaturated; Fibroblast Growth Factor 2; Humans; Hydrazines; Lung Neoplasms; Lymphokines; Male; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Neoplasm Metastasis; Neovascularization, Pathologic; Rats; Receptors, Thromboxane; Thromboxane A2; Thromboxane-A Synthase; Umbilical Veins; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

This study investigates whether phorbol esters increase phosphoinositide hydrolysis in intact vascular smooth muscle, and the mechanism underlying the hydrolysis. Phorbol myristate acetate induced time- and concentration-dependent increases in phosphoinositide hydrolysis, as demonstrated by elevated inositol monophosphate levels, in deendothelialized rat aorta. The phorbol ester-elevated inositol monophosphate levels were abolished by indomethacin, a cyclooxygenase inhibitor, but were only partially decreased by SQ29548, a thromboxane A2/prostaglandin H2 receptor antagonist. SQ29548 also only partially decreased elevated inositol monophosphate levels due to prostaglandin E2, prostaglandin F2alpha, prostaglandin I2 and carbacyclin, a stable prostaglandin I2 analog. SQ29548 abolished elevated inositol monophosphate levels due to U46619, a stable thromboxane A2/prostaglandin H2 receptor agonist. These studies demonstrate that phorbol esters increase phosphoinositide hydrolysis in intact vascular smooth muscle, and that the increase is due, at lease in part, to endogenously released prostaglandins other than prostaglandin H2.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aorta, Thoracic; Bridged Bicyclo Compounds, Heterocyclic; Epoprostenol; Fatty Acids, Unsaturated; Hydrazines; Hydrolysis; Indomethacin; Inositol Phosphates; Muscle, Smooth, Vascular; Phosphatidylinositols; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Rats; Rats, Sprague-Dawley; Signal Transduction; Tetradecanoylphorbol Acetate

1. Comparison of the rank order of potency of the natural prostanoids prostaglandin E2 (PGE2), PGD2, PGF2 alpha and carbaprostacyclin in stimulating cyclic AMP in Jurkat cells is consistent with the presence of an EP receptor. 2. Lack of responsiveness to the EP1/EP3 selective agonist, sulprostone, and the EP2 agonists, butaprost and AH 13205, indicates that this receptor is not of the EP1, EP2 or EP3 subtypes. 3. Inhibition of PGE2-stimulated cyclic AMP by the EP4 antagonist, AH 23848 is non-competitive, unlike the competitive antagonism reported in the pig saphenous vein EP4 preparation. Furthermore, 16,16-dimethyl PGE2 is 100 fold less potent than PGE2 in Jurkat cells, while these agonists are equipotent in the rabbit jugular vein purported EP4 preparation. In addition, 1-OH PGE1, which also is active in the rabbit jugular vein preparation, is inactive in Jurkat cells at concentrations up to 1 x 10(-4) M. These data are not wholly consistent with any adenylate cyclase coupled EP receptor described to date. 4. It is postulated that an EP receptor, positively coupled to adenylate cyclase, with a unique pharmacological profile is present in Jurkat cells.

Topics: Adenylyl Cyclases; Animals; Biphenyl Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cyclic AMP; Dinoprost; Dinoprostone; Epoprostenol; Fatty Acids, Unsaturated; Humans; Hydrazines; Leukemia, T-Cell; Prostaglandin D2; Rabbits; Receptors, Prostaglandin E; Swine; T-Lymphocytes; Tumor Cells, Cultured

This study tests the hypothesis that prostaglandins (PGs) released in response to phorbol esters act as modulators of the phorbol ester-induced smooth muscle contraction. The rate and magnitude of the phorbol 12-myristate 13-acetate (PMA)-induced contraction of deendothelialized rat aorta were decreased by the cyclooxygenase inhibitor, indomethacin. The thromboxane (Tx) A2/PGH2 receptor antagonist, SQ-29548, also inhibited PMA-induced contraction, and the magnitude of inhibition was greater than that due to indomethacin. PMA induced the release of PGI2, PGE2, PGF2 alpha, and arachidonic acid, but not TxA2. The amount of PGI2 released was greater than that of PGE2 and PGF2 alpha. Indomethacin blocked the PMA-induced release of PG, but not of arachidonic acid. In PMA-contracted tissues, PGF2 alpha, PGE2, and the stable PGI2 and PGH2 analogues, carbacyclin and U-46619, respectively, induced further contraction. Pretreatment of PMA-contracted tissues with SQ-29548 partially inhibited the PGF2 alpha- and PGE2-induced contractions, completely inhibited contraction to U-46619, and reversed the carbacyclin-induced contraction to relaxation. These results demonstrate that, in rat aorta, PMA induces the release of PGs that exert both contractile and relaxant effects but whose net effect is to accelerate and augment the contraction induced by PMA. The PG-induced increase in PMA contraction is mediated, in large part, through TxA2/PGH2 receptor activation. The ability of various PGs, including carbacyclin, to activate the TxA2/PGH2 receptor suggests that one or more of these PGs, in addition to, presumably, PGH2, may be responsible for the increase in PMA contraction. PGI2 is the only endogenously released PG that can account for the relaxant effect.

Topics: Analysis of Variance; Animals; Aorta, Thoracic; Arachidonic Acid; Bridged Bicyclo Compounds, Heterocyclic; Epoprostenol; Fatty Acids, Unsaturated; Hydrazines; In Vitro Techniques; Indomethacin; Kinetics; Male; Models, Cardiovascular; Muscle Contraction; Muscle, Smooth, Vascular; Norepinephrine; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Prostaglandins, Synthetic; Rats; Rats, Sprague-Dawley; Tetradecanoylphorbol Acetate; Thromboxane A2; Time Factors

Prostaglandin (PG) I2 elicits a biphasic concentration-response curve in rat aorta: lower concentrations elicit relaxation, whereas at higher concentrations, the relaxation is reversed. The purpose of this study was to investigate 1) the nature of the receptors that mediate these effects and 2) whether the relaxant efficacy of PGI2 is decreased at higher PGI2 concentrations by PGI2-induced contraction. PGI2 (1 microM), the stable PGI2 analogue carbacyclin (1 microM), and PGE1 (3 microM) induced maximal relaxations of 55, 40, and 63%, respectively, of norepinephrine-contracted aorta, whereas higher concentrations of PGI2, carbacyclin, and PGE1 reversed the relaxation. The thromboxane (Tx) A2-PGH2 receptor antagonist, SQ-29548, abolished the reversal of the PGI2-, carbacyclin-, and PGE1-induced relaxation, and maximal relaxations to PGI2, carbacyclin, and PGE1 increased to 73, 85, and 89% of the norepinephrine contraction, respectively, with 50% effective concentrations of 0.16, 0.43, and 0.83 microM, respectively. PGE2 and PGD2 did not induce relaxation in the presence or absence of SQ-29548. PGI2 and carbacyclin displaced the TxA2-PGH2 receptor ligand 1S-[1 alpha,2 beta(5Z),3 alpha(1E,3S),4 alpha]-7-(3-[3-hydroxy-4-(p- [125I]iodophenoxy)-1-butenyl]7-oxabicyclo[2.2.1]hept-2-yl]-5- heptenoic acid from cultured rat aorta smooth muscle cells with concentrations of competing ligand that displaced 50% of the specifically bound radioligand from its binding site of 6.0 and 2.3 microM, respectively. These results suggest that 1) PGI2 induces relaxation through a PGI2-PGE1 receptor, and 2) higher concentrations of PGI2 act at the TxA2-PGH2 receptor to decrease PGI2-induced relaxation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cells, Cultured; Epoprostenol; Fatty Acids, Unsaturated; Hydrazines; Male; Muscle, Smooth, Vascular; Prostaglandin Endoperoxides, Synthetic; Prostaglandins; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Thromboxane A2; Vasoconstriction; Vasoconstrictor Agents; Vasomotor System