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D2-like-receptors agonist
Zt046, A NEW DOPAMINERGIC AGONIST WITH HIGH AFFINITY FOR D1-LIKE AND D2-LIKE RECEPTOR SUBTYPES M__~.Fantoni.C.Bisiani, C.Masotto, E.Moriggi, F.Pocchiari, C.Semeraro Zambon Group S.p.A.,Via L del Duca,10, 20091 Bresso (Milan), Italy.
BRADYKININ INCREASES VASCULAR PERMEABILITY IN THE HAMSTER CHEEK POUCH: ROLE OF NO. M. Ftlttou, E. Bonnardel and-E. Canet Dtpartement de Pneumologie, Institut de Recherches Servier, 11 rue des Moulineaux, 92150 Suresnes, France.
Whereas biochemical and pharmacological studies indicated that there were two subclasses of dopamine (DA) receptors D1 and D2, the application of molecular biology techniques has defined at least five different DA receptor isoforms. These have been classified into DI -like (D1 and D5 receptors) and 1:)2-like families(D2, D3 and D4 receptors). To date all the DA receptors present in the brain are identical to those expressed in peripheral tissues. Therefore to design a newand more active DA agonists we have to consider the existence of these DA receptor subtypes. Aim of this study was to investigate the DA receptor affinity and Dl-like receptor-mediated cAMP accumulation of a serie of aminotetralins, in comparison with DA, epinine (EPI), fenoldopam (FEN) and Z1046 i.e.(S)-6-[[6-[[2-(2-methoxyphenoxy)ethyl]amino] propyl]amino]-5,6,7,8-tetrahydro-l,2-naphtalenediol dihydrochlodde our new peripheral dopaminergic agonist. Chinese hamster ovary (CHO) cell lines expressing the five DA receptors were used. Radioreceptor binding studies were performed using [3H]-SCH 23390 and [3H]Spiperone as specific ligands for Dl-like and D2-1ike receptors, respectively. Within Dl-like family the observed affinity rank order is: Zt046=FEN>DP-5,6-ADTN >DA=EPI =6,7-ADTN>DP-6,7-ADTN>= 5,6 ADTN. The Dl-like mediated cAMP accumulation show for these compounds the same order of potency. For the D2-1ike receptors the affinity rank order for D2 is: Z1046>DP-5,6-ADTN>DP-6,7-ADTN>=6,7ADTN>FEN>=DA=EPI=5,6-ADTN; for D3: Z1046>=DP-6,7-ADTN=DP5,6-ADTN=6,7-ADTN>DA=EPI>5,6-ADTN=FEN; and for D4: Z1046= DP-5,6-ADTN>DA=EPI>FEN>5,6-ADTN. Binding studies ~'show that Z1046 possesses a high affinity for the five subtypes of DA receptor. Z1046 reveals also a potent activity in inducing D1- and D5-mediated cAMP accumulation. In conclusion considering its high receptor affinity and D1- and D2-1ike pharmacological activities, Z1046 could be considered an innovative agent potentially useful for the treatment of different cardiovascular diseases.
The objective of this work was to study, in the hamster cheek pouch, the role of NO release on bradykinin (BK)-induced microvascular leakage. The cheek pouch microcirculatory bed of the anaesthetized hamster was directly observed under microscope and vascular leakage was evidenced by dextran-fitc extravasation. BK, but not Des-Arg9BK, superfusion induced an increase in microvascular permeability (exclusively located on the post-capillary venules) which was blocked by pretreatment with Icatibant, a BK 2 receptor antagonist. The effects of BK were suppressed by pretreatment with L-nitro-arginine (LNA), the NO synthase inhibitor but were marginally affected by indomethacin, the cyclooxygenase inhibitor. Acetylcholine, which releases endothelial NO, sodium nitroprusside, a nitrovasodilator, cromakalim, a potassium channel opener and CGRP, an activator of adenylate cyclase, did not induce major changes in permeability p e r se. However, in presence of LNA, the changes in permeability induced by BK were restored by the addition of SNP, cromakalim or CGRP. Conversely vasoconstriction, produced by a stable analogue of thromboxane A2, impeded the increase in permeability produced by BK. Arteriolar diameter measurement showed that BK induced a vasodilatation which was blocked by LNA. LNA in itself was a powerful vasoconstrictor. SNP and cromakalim, in presence of LNA, were able to restore the inhibited vasodilatation to BK. These results suggest: 1) bradykinin-induced microvascular leakage is mediated by BK 2 receptor activation - 2) the increase in permeability might be due to two differrent independent phenomena, i.e. post-capillary venular endothelial "contraction" and arteriolar vasodilatation which increases the post-capillary venular transmural pressure - 3) NO is only involved in the arteriolar dilatation component of the BK-induced increase in micro~cascular permeability.
PERIPHERAL DOPAMINERGIC ACTIVITY OF Z1046, A NEW MIXED DI-LIKE/D2-UKE-RECEPTORS AGONIST P. Ferlen.qa, D. Zanzottera, F. Marchini, C. Semeraro Zambon Group S.p.a., Via L.del Duca, 10, 20091 Bresso (Milan) Italy.
DIFFERENT DISTRIBUTION OF SUBTYPES IN RAT PORTAL VEIN
RECEPTOR.
A. Filippelli, M. Falciani, A. Palla, M. D'Amico, C. Vaeca and F. Rossi Institute of Pharmacology and Toxicology, Faculty of Medicine and Surgery, II University of Naples - Via Costantinopoli 16 - 80138 Naples (Italy)
Z1046 is a mixed Dl-like/D2-1ike receptors agonist which evokes peripheral vasodilation. Unlike dopamine (DA), Z1046 lacks of ~1, 13 and 5-HT 2 agonist activity and has weak cx2 agonist and
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ENDOTHELIN-1
Endothelin-I (ET-I), a potent vaseactive peptide, was first isolated from cultured porcine endothelial cells. Subsequent studies have revealed the existence of two additional related peptides, ET-2 and ET-3, and at least two distinct ET receptor subtypes, ETA (selective for ET-I) and ETB 01on selective for ET-isOpeptides). The above-mentioned isopeptides and receptors are widely distributed in many tissues and are involved in numerous biological responses. The aim of this study was to identify tile distribution of the two distinct endothelin receptor subtypes in isolated endothelium-denuded rat portal vein rings (PVR) and strips (PVS). For the differentiation of the subtypes, BQI23 (0.6, 1 and 6glvl) and PD145065 (0.06, 0.1, 0.6 and 6pM), respectively ETA selective and ETA/ET B non selective receptor antagonists, were used. In PVR cumulative additions of ET-I (0.I nM to 100 nM) caused graded and slow contractions, and potentiated spontaneous contractions. The EC50 values and maximal response (Emax) to 100 nM ET-I were 2.72 ruM and 0.75 g respectively (n = 7). PVS showed ET-1 EC50 values very similar to PVR, vice versa Emax values to 100 nM of ET-1 were significantly lower (Emax = 0.33 g; p < 0.01 vs PVR) (n = 7). Moreover, ET-1 deafly increased the amplitude and frequency of spontaneous contractions in both types of specimens, although these were greater in the PVS. 30 rain incubation with the selective ETA receptor antagonist BQ 123 while blunted ET-1 induced effects in PVS specimens, it only weakly antagonized ET-1 induced contractions in PVR. In contrast, the non selective ETA/ET B receptor antagonist, PD145065, whereas significantly shifted ET-I concentrationresponse curve to the right in PVR, it partially inhibited ET-1 effects in PVS. These data suggest that ETA and ETB receptors coexist in rat isolated portal vein and stimulation of both receptor subtypes contributes to ET-induced contraction in this tissue. The differences observed in PVS specimens in response to ET-I and the ability of BQ 123 to revert this effect may be explaiued by different distribution of receptor subtypes. In the rat PVR ETB receptors may be better expressed than in PVS.
243
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BRADYKININ INCREASES VASCULAR PERMEABILITY IN THE HAMSTER CHEEK POUCH: ROLE OF NO. M. Ftlttou, E. Bonnardel and-E. Canet Dtpartement de Pneumologie, Institut de Recherches Servier, 11 rue des Moulineaux, 92150 Suresnes, France.
Whereas biochemical and pharmacological studies indicated that there were two subclasses of dopamine (DA) receptors D1 and D2, the application of molecular biology techniques has defined at least five different DA receptor isoforms. These have been classified into DI -like (D1 and D5 receptors) and 1:)2-like families(D2, D3 and D4 receptors). To date all the DA receptors present in the brain are identical to those expressed in peripheral tissues. Therefore to design a newand more active DA agonists we have to consider the existence of these DA receptor subtypes. Aim of this study was to investigate the DA receptor affinity and Dl-like receptor-mediated cAMP accumulation of a serie of aminotetralins, in comparison with DA, epinine (EPI), fenoldopam (FEN) and Z1046 i.e.(S)-6-[[6-[[2-(2-methoxyphenoxy)ethyl]amino] propyl]amino]-5,6,7,8-tetrahydro-l,2-naphtalenediol dihydrochlodde our new peripheral dopaminergic agonist. Chinese hamster ovary (CHO) cell lines expressing the five DA receptors were used. Radioreceptor binding studies were performed using [3H]-SCH 23390 and [3H]Spiperone as specific ligands for Dl-like and D2-1ike receptors, respectively. Within Dl-like family the observed affinity rank order is: Zt046=FEN>DP-5,6-ADTN >DA=EPI =6,7-ADTN>DP-6,7-ADTN>= 5,6 ADTN. The Dl-like mediated cAMP accumulation show for these compounds the same order of potency. For the D2-1ike receptors the affinity rank order for D2 is: Z1046>DP-5,6-ADTN>DP-6,7-ADTN>=6,7ADTN>FEN>=DA=EPI=5,6-ADTN; for D3: Z1046>=DP-6,7-ADTN=DP5,6-ADTN=6,7-ADTN>DA=EPI>5,6-ADTN=FEN; and for D4: Z1046= DP-5,6-ADTN>DA=EPI>FEN>5,6-ADTN. Binding studies ~'show that Z1046 possesses a high affinity for the five subtypes of DA receptor. Z1046 reveals also a potent activity in inducing D1- and D5-mediated cAMP accumulation. In conclusion considering its high receptor affinity and D1- and D2-1ike pharmacological activities, Z1046 could be considered an innovative agent potentially useful for the treatment of different cardiovascular diseases.
The objective of this work was to study, in the hamster cheek pouch, the role of NO release on bradykinin (BK)-induced microvascular leakage. The cheek pouch microcirculatory bed of the anaesthetized hamster was directly observed under microscope and vascular leakage was evidenced by dextran-fitc extravasation. BK, but not Des-Arg9BK, superfusion induced an increase in microvascular permeability (exclusively located on the post-capillary venules) which was blocked by pretreatment with Icatibant, a BK 2 receptor antagonist. The effects of BK were suppressed by pretreatment with L-nitro-arginine (LNA), the NO synthase inhibitor but were marginally affected by indomethacin, the cyclooxygenase inhibitor. Acetylcholine, which releases endothelial NO, sodium nitroprusside, a nitrovasodilator, cromakalim, a potassium channel opener and CGRP, an activator of adenylate cyclase, did not induce major changes in permeability p e r se. However, in presence of LNA, the changes in permeability induced by BK were restored by the addition of SNP, cromakalim or CGRP. Conversely vasoconstriction, produced by a stable analogue of thromboxane A2, impeded the increase in permeability produced by BK. Arteriolar diameter measurement showed that BK induced a vasodilatation which was blocked by LNA. LNA in itself was a powerful vasoconstrictor. SNP and cromakalim, in presence of LNA, were able to restore the inhibited vasodilatation to BK. These results suggest: 1) bradykinin-induced microvascular leakage is mediated by BK 2 receptor activation - 2) the increase in permeability might be due to two differrent independent phenomena, i.e. post-capillary venular endothelial "contraction" and arteriolar vasodilatation which increases the post-capillary venular transmural pressure - 3) NO is only involved in the arteriolar dilatation component of the BK-induced increase in micro~cascular permeability.
PERIPHERAL DOPAMINERGIC ACTIVITY OF Z1046, A NEW MIXED DI-LIKE/D2-UKE-RECEPTORS AGONIST P. Ferlen.qa, D. Zanzottera, F. Marchini, C. Semeraro Zambon Group S.p.a., Via L.del Duca, 10, 20091 Bresso (Milan) Italy.
DIFFERENT DISTRIBUTION OF SUBTYPES IN RAT PORTAL VEIN
RECEPTOR.
A. Filippelli, M. Falciani, A. Palla, M. D'Amico, C. Vaeca and F. Rossi Institute of Pharmacology and Toxicology, Faculty of Medicine and Surgery, II University of Naples - Via Costantinopoli 16 - 80138 Naples (Italy)
Z1046 is a mixed Dl-like/D2-1ike receptors agonist which evokes peripheral vasodilation. Unlike dopamine (DA), Z1046 lacks of ~1, 13 and 5-HT 2 agonist activity and has weak cx2 agonist and
- -
ENDOTHELIN-1
Endothelin-I (ET-I), a potent vaseactive peptide, was first isolated from cultured porcine endothelial cells. Subsequent studies have revealed the existence of two additional related peptides, ET-2 and ET-3, and at least two distinct ET receptor subtypes, ETA (selective for ET-I) and ETB 01on selective for ET-isOpeptides). The above-mentioned isopeptides and receptors are widely distributed in many tissues and are involved in numerous biological responses. The aim of this study was to identify tile distribution of the two distinct endothelin receptor subtypes in isolated endothelium-denuded rat portal vein rings (PVR) and strips (PVS). For the differentiation of the subtypes, BQI23 (0.6, 1 and 6glvl) and PD145065 (0.06, 0.1, 0.6 and 6pM), respectively ETA selective and ETA/ET B non selective receptor antagonists, were used. In PVR cumulative additions of ET-I (0.I nM to 100 nM) caused graded and slow contractions, and potentiated spontaneous contractions. The EC50 values and maximal response (Emax) to 100 nM ET-I were 2.72 ruM and 0.75 g respectively (n = 7). PVS showed ET-1 EC50 values very similar to PVR, vice versa Emax values to 100 nM of ET-1 were significantly lower (Emax = 0.33 g; p < 0.01 vs PVR) (n = 7). Moreover, ET-1 deafly increased the amplitude and frequency of spontaneous contractions in both types of specimens, although these were greater in the PVS. 30 rain incubation with the selective ETA receptor antagonist BQ 123 while blunted ET-1 induced effects in PVS specimens, it only weakly antagonized ET-1 induced contractions in PVR. In contrast, the non selective ETA/ET B receptor antagonist, PD145065, whereas significantly shifted ET-I concentrationresponse curve to the right in PVR, it partially inhibited ET-1 effects in PVS. These data suggest that ETA and ETB receptors coexist in rat isolated portal vein and stimulation of both receptor subtypes contributes to ET-induced contraction in this tissue. The differences observed in PVS specimens in response to ET-I and the ability of BQ 123 to revert this effect may be explaiued by different distribution of receptor subtypes. In the rat PVR ETB receptors may be better expressed than in PVS.
243
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