Childhood Sexual Abuse, Dyadic Empathy, and Intimate Partner Violence Among Men Seeking Psychological Help

Childhood sexual abuse (CSA) and intimate partner violence (IPV) have both been associated with numerous negative repercussions. The first aim of this study is to understand IPV perpetrated by men within a clinical population, by examining the effects of two potential predictors: CSA and dyadic empathy (cognitive and emotional). The second aim of this study is to explore whether dyadic empathy is an intermediary variable of the association between CSA and IPV. A sample of 198 men (aged 18-69 years old) who were seeking help for relationship problems, completed a set of self-administered questionnaires. While controlling for social desirability and family violence history, our findings outlined the mediating and moderating role of dyadic empathy in the link between CSA and perpetrated psychological, but not physical, IPV. Emotional empathy mediated and moderated the link between CSA and psychological IPV, whereas cognitive empathy only moderated this link. The examination of the direct links between the variables also revealed that CSA was related to lower emotional empathy and higher rates of both types of IPV. In addition, cognitive empathy was negatively associated with physical and psychological IPV, whereas emotional empathy was positively associated with psychological IPV. This study contributes to the literature by documenting some of the mechanisms that could explain the perpetration of IPV and highlights the importance of investigating CSA and empathy in men who are seeking help.

Intimate Partner Violence Perpetrated by Men Seeking Help: The Explanatory Roles of Psychological Distress and Affect Dysregulation

Despite an increase in research initiatives and prevention campaigns, intimate partner violence (IPV) remains a public health problem that affects many victims worldwide. The current study aims to examine whether psychological distress symptoms (anger, depression, and anxiety) are indirectly related to the perpetration of IPV (physical assault, psychological abuse, and coercive control) through affect dysregulation (AD) in men seeking help. Online questionnaires assessing psychological distress symptoms, AD, and violent behaviors were completed by 335 adult men entering treatment for IPV. A path analysis model revealed the indirect associations between psychological distress symptoms and higher IPV perpetration through higher AD. Symptoms of anger were indirectly related to the three forms of perpetrated IPV through higher AD. Symptoms of depression were, directly and indirectly, related to the three forms of perpetrated IPV through higher AD. Finally, symptoms of anxiety were directly related to lower physical assault perpetration, and indirectly related to higher physical assault and coercive control perpetration through higher AD. The final model explained 10% of the variance in perpetrated physical assault, 23% of the variance in perpetrated psychological abuse, and 13% of the variance in perpetrated coercive control. These results underline the necessity of assessing and addressing symptoms of psychological distress and AD among men perpetrators in the treatment of IPV.

Attachment Insecurities and Sexual Coercion in Same- and Cross-Gender Couples: The Mediational Role of Couple Communication Patterns

The use of subtle strategies to have sex with an unwilling partner is harmful to a couple's sexual well-being but these strategies remain understudied. This research examined the mediating role of communication patterns in the associations between attachment insecurities and sustained sexual coercion in 145 same- and cross-gender couples, and the moderating role of partners' gender. In addition to actor and partner effects, results revealed significant indirect effects from attachment insecurities to sexual coercion via communication patterns, with moderating effects of gender. Results may help practitioners and researchers understand the ways attachment insecurities and dysfunctional communication patterns can manifest in the experience of subtle forms of sexual coercion within couples.

ARF1 controls proliferation of breast cancer cells by regulating the retinoblastoma protein

The ADP-ribosylation factors (ARFs) 1 and 6 are small GTP-binding proteins, highly expressed and activated in several breast cancer cell lines and are associated with enhanced migration and invasiveness. In this study, we report that ARF1 has a critical role in cell proliferation. Depletion of this GTPase or expression of a dominant negative form, which both resulted in diminished ARF1 activity, led to sustained cell-growth arrest. This cellular response was associated with the induction of senescent markers in highly invasive breast cancer cells as well as in control mammary epithelial cells by a mechanism regulating retinoblastoma protein (pRB) function. When examining the role of ARF1, we found that this GTPase was highly activated in normal proliferative conditions, and that a limited amount could be found in the nucleus, associated with the chromatin of MDA-MB-231 cells. However, when cells were arrested in the G(0)/G(1) phase or transfected with a dominant negative form of ARF1, the total level of activated ARF1 was markedly reduced and the GTPase significantly enriched in the chromatin. Using biochemical approaches, we demonstrated that the GDP-bound form of ARF1 directly interacted with pRB, but not other members of this family of proteins. In addition, depletion of ARF1 or expression of ARF1T(31)N resulted in the constitutive association of pRB and E2F1, thereby stabilizing the interaction of E2F1 as well as pRB at endogenous sites of target gene promoters, preventing expression of E2F target genes, such as cyclin D1, Mcm6 and E2F1, important for cell-cycle progression. These novel findings provide direct physiological and molecular evidence for the role of ARF1 in controlling cell proliferation, dependent on its ability to regulate pRB/E2F1 activity and gene expression for enhanced proliferation and breast cancer progression.

Binding of the beta2 adrenergic receptor to N-ethylmaleimide-sensitive factor regulates receptor recycling

Following agonist stimulation, most G protein-coupled receptors become desensitized and are internalized, either to be degraded or recycled back to the cell surface. What determines the fate of a specific receptor type after it is internalized is poorly understood. Here we show that the rapidly recycling beta2 adrenergic receptor (beta2AR) binds via a determinant including the last three amino acids in its carboxyl-terminal tail to the membrane fusion regulatory protein, N-ethylmaleimide-sensitive factor (NSF). This is documented by in vitro overlay assays and by cellular coimmunoprecipitations. Receptors bearing mutations in any of the last three residues fail to interact with NSF. After stimulation with the agonist isoproterenol, a green fluorescent protein fusion of NSF colocalizes with the wild type beta2AR but not with a tail-mutated beta2AR. The beta2AR-NSF interaction is required for efficient internalization of the receptors and for their recycling to the cell surface. Mutations in the beta2AR tail that ablate NSF binding reduce the efficiency of receptor internalization upon agonist stimulation. Upon subsequent treatment of cells with the antagonist propranolol, wild type receptors return to the cell surface, while tail-mutated receptors remain sequestered. Thus, the direct binding of the beta2AR to NSF demonstrates how, after internalization, the fate of a receptor is reliant on a specific interaction with a component of the cellular membrane-trafficking machinery.

beta-Arrestin-mediated ADP-ribosylation factor 6 activation and beta 2-adrenergic receptor endocytosis

beta-Arrestins are multifunctional adaptor proteins known to regulate internalization of agonist-stimulated G protein-coupled receptors by linking them to endocytic proteins such as clathrin and AP-2. Here we describe a previously unappreciated mechanism by which beta-arrestin orchestrates the process of receptor endocytosis through the activation of ADP-ribosylation factor 6 (ARF6), a small GTP-binding protein. Involvement of ARF6 in the endocytic process is demonstrated by the ability of GTP-binding defective and GTP hydrolysis-deficient mutants to inhibit internalization of the beta(2)-adrenergic receptor. The importance of regulation of ARF6 function is shown by the ability of the ARF GTPase-activating protein GIT1 to inhibit and of the ARF nucleotide exchange factor, ARNO, to enhance receptor endocytosis. Endogenous beta-arrestin is found in complex with ARNO. Upon agonist stimulation of the receptor, beta-arrestin also interacts with the GDP-liganded form of ARF6, thereby facilitating ARNO-promoted GTP loading and activation of the G protein. Thus, the agonist-driven formation of a complex including beta-arrestin, ARNO, and ARF6 provides a molecular mechanism that explains how the agonist-stimulated receptor recruits a small G protein necessary for the endocytic process and controls its activation.

The GIT family of ADP-ribosylation factor GTPase-activating proteins. Functional diversity of GIT2 through alternative splicing

We recently characterized a novel protein, GIT1, that interacts with G protein-coupled receptor kinases and possesses ADP-ribosylation factor (ARF) GTPase-activating protein activity. A second ubiquitously expressed member of the GIT protein family, GIT2, has been identified in data base searches. GIT2 undergoes extensive alternative splicing and exists in at least 10 and potentially as many as 33 distinct forms. The longest form of GIT2 is colinear with GIT1 and shares the same domain structure, whereas one major splice variant prominent in immune tissues completely lacks the carboxyl-terminal domain. The other 32 potential variants arise from the independent alternative splicing of five internal regions in the center of the molecule but share both the amino-terminal ARF GTPase-activating protein domain and carboxyl-terminal domain. Both the long and short carboxyl-terminal variants of GIT2 are active as GTPase-activating proteins for ARF1, and both also interact with G protein-coupled receptor kinase 2 and with p21-activated kinase-interacting exchange factors complexed with p21-activated kinase but not with paxillin. Cellular overexpression of the longest variant of GIT2 leads to inhibition of beta(2)-adrenergic receptor sequestration, whereas the shortest splice variant appears inactive. Although GIT2 shares many properties with GIT1, it also exhibits both structural and functional diversity due to tissue-specific alternative splicing.

Multiple endocytic pathways of G protein-coupled receptors delineated by GIT1 sensitivity

Recently, we identified a GTPase-activating protein for the ADP ribosylation factor family of small GTP-binding proteins that we call GIT1. This protein initially was identified as an interacting partner for the G protein-coupled receptor kinases, and its overexpression was found to affect signaling and internalization of the prototypical beta(2)-adrenergic receptor. Here, we report that GIT1 overexpression regulates internalization of numerous, but not all, G protein-coupled receptors. The specificity of the GIT1 effect is not related to the type of G protein to which a receptor couples, but rather to the endocytic route it uses. GIT1 only affects the function of G protein-coupled receptors that are internalized through the clathrin-coated pit pathway in a beta-arrestin- and dynamin-sensitive manner. Furthermore, the GIT1 effect is not limited to G protein-coupled receptors because overexpression of this protein also affects internalization of the epidermal growth factor receptor. However, constitutive agonist-independent internalization is not regulated by GIT1, because transferrin uptake is not affected by GIT1 overexpression. Thus, GIT1 is a protein involved in regulating the function of signaling receptors internalized through the clathrin pathway and can be used as a diagnostic tool for defining the endocytic pathway of a receptor.

beta2-Adrenergic receptor regulation by GIT1, a G protein-coupled receptor kinase-associated ADP ribosylation factor GTPase-activating protein

G protein-coupled receptor activation leads to the membrane recruitment and activation of G protein-coupled receptor kinases, which phosphorylate receptors and lead to their inactivation. We have identified a novel G protein-coupled receptor kinase-interacting protein, GIT1, that is a GTPase-activating protein (GAP) for the ADP ribosylation factor (ARF) family of small GTP-binding proteins. Overexpression of GIT1 leads to reduced beta2-adrenergic receptor signaling and increased receptor phosphorylation, which result from reduced receptor internalization and resensitization. These cellular effects of GIT1 require its intact ARF GAP activity and do not reflect regulation of GRK kinase activity. These results suggest an essential role for ARF proteins in regulating beta2-adrenergic receptor endocytosis. Moreover, they provide a mechanism for integration of receptor activation and endocytosis through regulation of ARF protein activation by GRK-mediated recruitment of the GIT1 ARF GAP to the plasma membrane.

The beta2-adrenergic receptor interacts with the Na+/H+-exchanger regulatory factor to control Na+/H+ exchange

Stimulation of beta2-adrenergic receptors on the cell surface by adrenaline or noradrenaline leads to alterations in the metabolism, excitability, differentiation and growth of many cell types. These effects have traditionally been thought to be mediated exclusively by receptor activation of intracellular G proteins. However, certain physiological effects of beta2-adrenergic receptor stimulation, notably the regulation of cellular pH by modulation of Na+/H+ exchanger (NHE) function, do not seem to be entirely dependent on G-protein activation. We report here a direct agonist-promoted association of the beta2-adrenergic receptor with the Na+/H+ exchanger regulatory factor (NHERF), a protein that regulates the activity of the Na+/H+ exchanger type 3 (NHE3). NHERF binds to the beta2-adrenergic receptor by means of a PDZ-domain-mediated interaction with the last few residues of the carboxy-terminal cytoplasmic domain of the receptor. Mutation of the final residue of the beta2-adrenergic receptor from leucine to alanine abolishes the receptor's interaction with NHERF and also markedly alters beta2-adrenergic receptor regulation of NHE3 in cells without altering receptor-mediated activation of adenylyl cyclase. Our findings indicate that agonist-dependent beta2-adrenergic receptor binding of NHERF plays a role in beta2-adrenergic receptor-mediated regulation of Na+/H+ exchange.

Comparison of the pre- and post-capillary vascular reactivity in the rat and guinea pig perfused mesenteric bed

The present study reports the development and optimization of a new model by which the vasoactive properties of various agents can be monitored in the endothelium-intact pre- and post-capillary mesenteric vasculatures of the guinea pig. In contrast with the rat, the guinea pig pre-capillary mesenteric circulation responds to neurokinins via an endothelium-dependent vasodilation (ED50 for the NK-1 selective agonist, 20.2 pmol). In addition, in the rat as in the guinea pig mesenteric vasculature, kinins induced an endothelium-dependent vasodilation in the venous and arterial circuits. ED50 values for rat were arterial, 1.0 nmol, venous, 100 pmol; ED50 values for guinea pig were arterial, 5.5 pmol, venous, 1.9 pmol. The pharmacology of the receptors for these vasoactive agents (and others) as well as the localization of these entities is discussed. In addition, an interspecies comparison is made between the pre- and post-capillary vascular reactivity in the mesenteric circuit of the rat and guinea pig. Our studies should elucidate the pharmacodynamic properties of vasoactive agents in the pre- and post-capillary circulation and shed further light on the contribution of these agonists in hydrostatic force changes and in plasma extravasation phenomena.

Characterization of receptors for kinins and neurokinins in the arterial and venous mesenteric vasculatures of the guinea-pig

1. In the present work, we have studied the microvascular reactivity of the arterial and venous mesenteric beds of the guinea-pig to bradykinin, neurokinins and other agents. 2. The vasoactive properties of three selective agonists for neurokinin receptors, namely [Sar9, Met (O2)11]SP (NK1), [beta-Ala8]NKA(4-10) (NK2) and [MePhe7]NKB (NK3), were evaluated on precontracted arterial and venous mesenteric vasculatures of the guinea-pig. The NK1-selective agonist, [Sar9,Met(O2)11]SP (1 to 1000 pmol), induced an endothelium-dependent and N omega-nitro-L-arginine methyl ester (L-NAME)-sensitive relaxation of the arterial vasculature precontracted with methoxamine, whereas the NK2 and NK3-selective agonists were virtually inactive at high doses (1000 pmol). 3. The three selective neurokinin receptor agonists were inactive in the non-precontracted arterial and venous mesenteric vasculatures as well as in the precontracted venous mesenteric vasculature. 4. Bradykinin (0.1 to 100 pmol) induced a marked dose- and endothelium-dependent vasodilatation of the precontracted arterial and venous vasculatures. ED50 values were 5.5 pmol on the arterial side and 1.9 pmol on the venous side. In contrast, desArg9-bradykinin was inactive at doses up to 1000 pmol. Furthermore, on the arterial and venous sides, a higher dose of bradykinin (1000 pmol), induced a biphasic effect, a transient constriction followed by a marked and sustained vasodilatation. The vasodilator effects of bradykinin were abolished by Hoe 140 (0.1 microM) and CHAPS, markedly reduced by L-NAME and were unaffected by [Leu8]desArg9-bradykinin (0.1 microM) on both sides of the mesenteric vasculature. Hoe 140 also abolished the arterial vasoconstrictions induced by high doses of bradykinin. 5. Noradrenaline, angiotensin II and endothelin-1 produced contractions on both sides of the mesenteric circulation, while acetylcholine (arterial side) and sodium nitroprusside (arterial and venous sides) caused vasodilatation.6. Our study supports the view that NK1 receptors responsible for vasodilatation are present solely in the endothelium of the arterial mesenteric vasculature of the guinea-pig. On the other hand, bradykinin(0.1 to 100 pmol) exerts predominantly vasodilator effects on both sides of the mesenteric vasculature via selective activation of B2 receptors located on the endothelium. The same receptor type located on the smooth muscle appears to be responsible for the arterial and venous constriction with high doses of bradykinin.

Rat adrenomedullin induces a selective arterial vasodilation via CGRP1 receptors in the double-perfused mesenteric bed of the rat

The present work was undertaken to study the effect of rat adrenomedullin (rADM (1-50) and its C-terminal fragment (11-50)) in the endothelium-intact arterial and venous vasculatures of the rat perfused mesenteric bed. rADM (1-50) and the fragment rADM (11-50)(1-1000 pmol) induced a dose-dependent and endothelium-independent vasodilation on the arterial mesenteric vasculature. However, both peptides were inactive on the venous side of this vascular bed. The CGRP1 receptor antagonist, hCGRP8-37 (1 microM), markedly reduced the vasodilation caused by rADM (1-50) in the arterial mesenteric vasculature. Thus, our results show that rADM (1-50) in the arterial mesenteric vasculature. Thus, our results show that rADM (1-50) and its C-terminal fragment rADM(11-50) share properties similar to those of hCGRP. The blocking effect of hCGRP8-37 supports a role for CGRP1 receptor activation by adrenomedullin in this vascular preparation.

Roles of peptides and other substances in cotransmission from vascular autonomic and sensory neurons

Blood vessels may be innervated by up to three major classes of neurons: sympathetic vasoconstrictor neurons; sympathetic or parasympathetic vasodilator neurons; and peripheral fibres of small diameter sensory neurons, which can mediate vasodilation. Most vascular neurons utilise multiple transmitters, including neuropeptides and small nonpeptides such as ATP or nitric oxide, often in addition to noradrenaline or acetylcholine. Subpopulations of each major class of vascular neurons innervating different vascular segments may contain different combinations of neurotransmitters. Furthermore, the same population of neurons can release different cotransmitters in response to different patterns of stimulation. In general, peptides mediate slower and more long lasting changes in vascular resistance than do nonpeptides. Thus, autonomic and sensory neurons are well adapted to produce qualitatively different vascular effects in response to different types of afferent input. The major challenge for the future is to develop new antagonists for many of the substances colocalised in vascular neurons, particularly neuropeptides. These agents will allow us to precisely determine the relative roles of multiple cotransmitters, and are likely to provide therapeutic agents that can be targeted to specific regions of the vasculature.

Processing of proendothelin-1 by human furin convertase

Endothelin-1 (ET-1) is the most potent vasoactive peptide known to date. The peptide is initially synthesized as an inactive precursor (proET-1) which undergoes proteolysis at specific pairs of basic amino acids to yield bigET-1. Production of ET-1 then proceeds by cleavage of bigET-1 by the endothelin converting enzyme (ECE). Here, we demonstrate that the in vitro cleavage of proET-1 by furin, a mammalian convertase involved in precursor processing, produced bigET-1. Upon further processing, bigET-1 was converted to biologically active ET-1. Furthermore, we demonstrate that the furin inhibitor, decanoyl-Arg-Val-Lys-Arg chloromethylketone, abolished production of ET-1 in endothelial cells.

Different pressor and bronchoconstrictor properties of human big-endothelin-1, 2 (1-38) and 3 in ketamine/xylazine-anaesthetized guinea-pigs

1. In the present study, the precursors of endothelin-1, endothelin-2 and endothelin-3 were tested for their pressor and bronchoconstrictor properties in the anaesthetized guinea-pig. In addition, the effects of big-endothelin-1 and endothelin-1 were assessed under urethane or ketamine/xylazine anaesthesia. 2. When compared to ketamine/xylazine, urethane markedly depressed the pressor and bronchoconstrictor properties of endothelin-1 and big-endothelin-1. 3. Under ketamine/xylazine anaesthesia, the three endothelins induced a biphasic increase of mean arterial blood pressure. In contrast, big-endothelin-1, as well as big-endothelin-2 (1-38), induced only sustained increase in blood pressure whereas big-endothelin-3 was inactive at doses up to 25 nmol kg-1. 4. Big-endothelin-1, but not big-endothelin-2, induced a significant increase in airway resistance. Yet, endothelin-1, endothelin-2 and endothelin-3 were equipotent as bronchoconstrictor agents. 5. Big-endothelin-1, endothelin-1 and endothelin-2, but not big-endothelin-2, triggered a marked release of prostacyclin and thromboxane A2 from the guinea-pig perfused lung. 6. Our results suggest the presence of a phosphoramidon-sensitive endothelin-converting enzyme (ECE) which is responsible for the conversion of big-endothelin-1 and big-endothelin-2 to their active moieties, endothelin-1 and 2. However, the lack of bronchoconstrictor and eicosanoid-releasing properties of big-endothelin-2, as opposed to endothelin-2 or big-endothelin-1, suggests the presence of two distinct phosphoramidon-sensitive ECEs in the guinea-pig. The ECE responsible for the systemic conversion of big-endothelins possesses the same affinity for big-endothelin-l and 2 but not big-endothelin-3. In contrast, in the pulmonary vasculature is localized in the vicinity of the sites responsible for eicosanoid release, an ECE which converts more readily big-endothelin-1 than big-endothelin-2.

Block of endothelin-1-induced release of thromboxane A2 from the guinea pig lung and nitric oxide from the rabbit kidney by a selective ETB receptor antagonist, BQ-788

1. The present study characterizes the receptors responsible for endothelin-1-induced release of thromboxane A2 from the guinea pig lung and of endothelium-derived nitric oxide from the rabbit perfused kidney, by the use of the selective ETA receptor antagonist, BQ-123, and a novel selective ETB receptor antagonist, BQ-788. 2. In the guinea pig perfused lung, endothelin-1 (ET-1) (5 nM) induced a marked increase of thromboxane A2 which was reduced by 17 +/- 5.0, 70 +/- 1.0 and 93 +/- 1.2% by BQ-788 infused at concentrations of 1, 5 and 10 nM respectively. In contrast, BQ-123 (0.1 and 1.0 microM) had little or no effect on the ET-1-induced release of thromboxane A2. 3. In the same perfused model, the selective ETB agonist, IRL 1620 (50 nM), stimulated the release of thromboxane A2, but not prostacyclin. The eicosanoid-releasing properties of IRL 1620 were abolished by BQ-788 at 10 nM, yet were unaffected by BQ-123 (1 microM). 4. In the rabbit perfused kidney, BQ-788 (10 nM) potentiated the increase of perfusion pressure induced by endothelin-1 (1, 5 and 10 nM) by approximately 90%, but not that induced by angiotensin II (1 microM). Furthermore, the selective ETB receptor antagonist did not reduce the release of prostacyclin triggered by either peptide. 5. In another series of experiments, pretreatment of the perfused kidney with a nitric oxide synthase inhibitor, L-NAME (100 microM), potentiated the pressor responses to both endothelin-1 and angiotensin II. Under L-NAME treatment, BQ-788 did not further potentiate the pressor response to endothelin-1. 6 Our results illustrate the predominant role of ETB receptor activation in the release of thromboxane A2 and nitric oxide triggered by endothelin-l in the guinea pig perfused lung and rabbit kidney respectively.

Role of R-type calcium channels in the response of the perfused arterial and venous mesenteric vasculature of the rat to platelet-activating factor

1. The vasoactive properties of platelet-activating factor (PAF) were studied in the arterial and venous vasculature of the rat double-perfused mesenteric bed. Although PAF (0.01-0.3 pmol) induced a dose-dependent vasodilatation of the arterial mesenteric vasculature, it triggered only vasoconstrictions on the venous side, with an intact endothelium as bradykinin induced a significant venodilatation. 2. NG-nitro-L-arginine methyl ester (L-NAME, 100 microM), a nitric oxide synthase inhibitor, markedly reduced the vasodilatation induced by PAF in the arterial mesenteric vasculature and potentiated the contractile responses of the venous side to the same agent. 3. The PAF antagonist, WEB-2170, markedly reduced the response to PAF on both sides of the mesenteric vasculature. However, the IC50 of WEB-2170 against PAF was reached at a much higher concentration (1 x 10(-8) M) on the arterial side than on the venous side (5.3 x 10(-11) M). Furthermore, a second antagonist of PAF receptors, SRI-63441, although being less potent on the venous vasculature than WEB-2170, was equipotent in antagonizing the venoconstriction and the arterial dilatation induced by PAF (IC50 of SRI-63441, arterial side: 2.9 x 10(-9) M; venous side: 3.1 x 10(-9) M). 4. The dual L- and R-calcium channel blocker, isradipine (PN 200-110), but not the L-type calcium channel blocker, nifedipine, markedly reduced the PAF-induced vasoactive properties on both sides of the mesenteric vasculature. 5. Our results illustrate the differential vasoactive properties of PAF in the mesenteric vasculature of the rat. These vasoactive responses occur following activation of specific receptors for PAF or,alternatively, through activation of R-type calcium channels.

Characterization of receptors for endothelins in the perfused arterial and venous mesenteric vasculatures of the rat

1. Endothelin-1 and -3 induced marked arterial and venous constrictions in the perfused mesenteric vasculature of the rat with endothelin-3 being at least 20 times less active than endothelin-1, on both arterial and venous sides of the vasculature. 2. Two ETB selective agonists, BQ-3020 and IRL 1620 (500 pmol), induced weak constrictions of the venous mesenteric vasculature and were inactive in the arterial side at doses up to 1000 pmol. 3. In mesenteric vasculatures precontracted with either methoxamine (arterial side) or the thromboxane A2-mimetic, U46619 (venous side), acetylcholine or bradykinin produced vasodilations of both arterial and venous vessels, whereas endothelin-3 induced vasodilations only on the arterial side. 4. A selective ETA receptor antagonist, BQ-123, blocked, in a concentration-dependent and reversible fashion, the vasoconstrictions induced by endothelin-1 on both sides of the mesenteric circulation (IC50; arterial side: 0.013 microM; venous side: 0.032 microM). 5. In contrast, the vasodilator responses induced by endothelin-3 on the arterial side of the precontracted mesenteric vasculature were not affected by BQ-123. 6. The present study illustrates the presence of ETA receptors which are responsible for vasoconstriction by endothelins in the arterial and venous mesenteric vasculatures. Furthermore, we suggest that the vasodilations induced by endothelin-3 in the arterial vasculature uniquely, are ETB receptor-mediated.

Endothelin-1 induces vasoconstriction and prostacyclin release via the activation of endothelin ETA receptors in the perfused rabbit kidney

Endothelin-1 (0.005 and 0.01 nmol) induced a dose-dependent increase in perfusion pressure in the perfused rabbit kidney. These pressor effects were markedly reduced by an endothelin ETA receptor antagonist, BQ-123 (0.1 microM). Similarly, the release of prostacyclin triggered by intra-arterial infusion of endothelin-1 (10 nM) was significantly reduced in a concentration-dependent manner when the kidney was pretreated with BQ-123 (0.5-1 microM). In contrast, two selective ETB receptor agonists, BQ-3020 and IRL 1620, were found to be inactive, both as pressor agents and releasers of prostacyclin at doses (for the pressor effects) and concentrations (for the prostacyclin generation) 50-100 times higher than those of endothelin-1. BQ-123 (1 microM) did not modify the pressor or prostanoid-releasing properties of angiotensin II. These results confirm our previous observations suggesting that pressor responses and prostanoid release induced by endothelin-1 are mediated via the selective activation of ETA receptors in the perfused rabbit kidney.

Pharmacologic evidence for the specificity of the phosphoramidon-sensitive endothelin-converting enzyme for big endothelin-1

The pharmacology of human big endothelin-1 (big ET-1) and big ET-3 was compared in five pharmacologic models: perfused rat and guinea pig lungs, perfused rabbit kidney, and in the rat and the guinea pig in vivo (blood pressure monitoring). In these models, big ET-1 consistently induced concentration- or dose-dependent pharmacologic effects sensitive to phosphoramidon (vasopressor or prostanoid-releasing effects). In contrast, big ET-3, dissolved in either phosphate-buffered saline (pH 7.4) or 0.1% acetic acid, was inactive in all the models used in this study. In addition, the activity of big ET-3 was also assessed in the prostatic portion of the rat vas deferens. In this model, although big ET-1 induced a phosphoramidon-sensitive increase of the twitch response of the tissue to electrical stimulation, big ET-3, dissolved either in phosphate-buffered saline or acetic acid, remained inactive. Our results, presented in the above-mentioned models, illustrate the capacity of the phosphoramidon-sensitive endothelin-converting enzyme (ECE) to discriminate between human big ET-1 and big ET-3.

Substance P (NK-1 receptor) antagonists: in vivo and in vitro activities in rats and guinea pigs

NK-1 receptor subtypes have been identified by the use of CP-96,345 and RP-67,580, two non-peptide antagonists. These and other antagonists have been tested in vivo and in vitro in guinea pigs and rats to counteract the hypotensive and contractile (urinary isolated bladder) effects of a) SP, b) the NK-1 selective agonist [Sar9,Met(O2)11]SP and c) other neurokinins. CP-96,345 has been found to be more active on the guinea pig and RP-67,580 more active on the rat by at least 1 log unit both in vivo and in vitro. Both compounds are selective NK-1 antagonists and RP-67,580 appears to be weaker than CP-96,345. Two in vitro preparations, the guinea pig and rat urinary bladder are proposed as bioassays for the NK-1A (guinea pig) and NK-1B (rat) receptor subtypes, which have been shown to mediate smooth muscle contraction and hypotension, resulting from peripheral vasodilatation. CP-96,345 and RP-67,580 are more potent antagonists than spantide, its homologous octapeptide and the Fujisawa tri or dipeptides.

Nonadrenergic and noncholinergic arterial dilatation and venoconstriction are mediated by calcitonin gene-related peptide1 and neurokinin-1 receptors, respectively, in the mesenteric vasculature of the rat after perivascular nerve stimulation

In the present study, selective calcitonin gene-related peptide (CGRP) and neurokinin (NK) agonists and antagonists were used to characterize the receptors mediating the nerve-induced arterial vasodilation and venous vasoconstriction in the rat mesenteric vasculature. In guanethidine-pretreated preparations, perivascular nerve stimulation (PNS) induced a frequency-dependent vasodilation in the arterial vasculature (precontracted with methoxamine), yet only induced an atropine-resistant contraction in the venous mesenteric vasculature (precontracted with U46619) of the rat. hCGRP alpha induced a marked dose-dependent relaxation of the arterial side, whereas only a slight vasodilation was seen at a high dose on the precontracted venous side. The PNS or hCGRP alpha-induced arterial dilatation was markedly reduced by the antagonist hCGRP8-37, whereas the venoconstrictive response to PNS was not. Furthermore, [acetamidomethyl-Cys2,7]hCGRP was inactive on either side of the rat mesenteric vasculature. A selective NK-1 nonpeptidic antagonist (CP-96,345) reduced the response of the venous vasculature to PNS by 70% without affecting the response of the arterial side to the same stimulus. Furthermore, a selective NK-3 receptor antagonist ([Trp7,beta-Ala8]-NKA (4-10)) did not affect the venoconstriction induced by PNS, yet markedly reduced the pressor response induced by a selective NK-3 receptor agonist, [MePhe7]-NKB. Hence, PNS induces the release of CGRP which activates specifically CGRP1 receptors and induces relaxation on the arterial vasculature. On the venous side, the nerve stimulation activates transmural NK-1 receptors and evokes a venoconstriction.

Phosphoramidon-sensitive effects of big endothelins in the perfused rabbit kidney

The enzymatic conversion of human big endothelins (1, 2, and 3) to their respective active metabolites (endothelin-1, -2, and -3) was investigated in the perfused rabbit kidney through the pressor- and eicosanoid-releasing properties of these peptides. Intra-arterial bolus injections of endothelin-1 and -2 (5-50 pmol), endothelin-3 (100-250 pmol), and big endothelin-1 and -2 (100-250 pmol) into the kidney produced dose-dependent increases of perfusion pressure, whereas big endothelin-3 was inactive at doses up to 1,000 pmol. Endothelin-1 and -2 (10 nM), endothelin-3 (100 nM), and big endothelin-1 and -2 (100 nM) are potent enhancers of prostacyclin release without inducing any release of thromboxane B2 in the perfused kidney. In contrast, big endothelin-3 did not trigger the release of eicosanoids. A metalloprotease inhibitor, phosphoramidon (100 microM, 60 minutes), reduced the prostanoid release and pressor responses induced by big endothelin-1 and -2 without affecting the response induced by endothelin-1, -2, and -3. These results suggest the presence of a phosphoramidon-sensitive endothelin converting enzyme that converts the precursors of endothelin-1 and -2, but not of endothelin-3, in the renal vasculature of the rabbit.

Human big-endothelin-1 and endothelin-1 release prostacyclin via the activation of ET1 receptors in the rat perfused lung

Although ET1 and ET2 binding sites were found in rat lung membranes, a selective ET1 receptor antagonist, BQ-123 (10 microM), did not displace [125I]-endothelin-1 ([125I]ET-1) from ET2 sites, illustrating the selectivity of the angatonist for ET1 receptors. In rat perfused lungs, BQ-123 (1 microM) markedly reduced the prostacyclin (PGI2) releasing properties of endothelin-1 (ET-1: 5 nM) and human big-ET-1 (100 nM) suggesting that both peptides induce the release of PGI2 via the selective activation of ET1 receptors.

Neurokinins produce selective venoconstriction via NK-3 receptors in the rat mesenteric vascular bed

The vasoactive properties of the neurokinins (substance P (SP), neurokinin A (NKA), neurokinin B (NKB)) and some selective analogues were assessed in the arterial and venous mesenteric beds of the rat. Although both sides of the mesenteric vasculature displayed endothelium-dependent relaxation in response to acetylcholine (ACh) or bradykinin (BK) (1 and 10 nmol), SP and the selective NK-1 analogue, [Sar9,Met(O2)11]SP were inactive. Of the three selective neurokinin agonists used, [Sar9,Met(O2)11]SP (NK-1), [beta-Ala8]NKA-(4-10) (NK-2) and [MePhe7]NKB (NK-3), only the latter induced a dose-dependent pressor effect in the venous mesenteric vasculature. Injections of SP and the selective NK-1 and NK-2 analogues at high doses (10 nmol), did not change the perfusion pressure in the mesenteric bed even when the mesenteric vasculature was treated with methylene blue (50 microM) to inhibit the effects of endothelium-derived relaxing factor (EDRF) or with NG-nitro-L-arginine (L-NNA) (20 microM) to inhibit the formation of EDRF or with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate] (CHAPS 20 mM, 30 s) to remove the endothelial layer. In contrast, the vasoconstrictor effects of noradrenaline (NA), angiotensin II (ATII), NKB and [MePhe7]NKB on the venous side of the circulation were enhanced following treatment with L-NNA, methylene blue or CHAPS. The present results suggest that neurokinins act on the rat mesenteric bed by increasing the perfusion pressure of the venous vasculature via activation of NK-3 receptors. Neurokinins are inactive on the arterial mesenteric vasculature.(ABSTRACT TRUNCATED AT 250 WORDS)

Different pharmacological profiles of big-endothelin-3 and big-endothelin-1 in vivo and in vitro

1. Human big-endothelin-1 (big-ET-1) and endothelin-1 (ET-1) are equipotent as pressor agents and produce a significant change in mean arterial blood pressure (MAP) in anaesthetized guinea-pigs (2 nmol kg-1: peak delta MAP: 23 +/- 6 mmHg and 26 +/- 5 mmHg, respectively). 2. Unlike big-ET-1, big-endothelin-3 (big-ET-3) (10 and 20 nmol kg-1) induces no pressor responses whereas endothelin-3 (ET-3) at 2 nmol kg-1 induces a significant increase of blood pressure in anaesthetized guinea-pigs (peak delta MAP: 27 +/- 5 mmHg) with a shorter duration than ET-1 and big-ET-1. 3. Big-ET-1 at concentrations 40 times higher than those required for ET-1 (2.5 nM) releases prostacyclin (PGI2) (maximal release: 2.7 +/- 0.8 ng ml-1; 2.9 +/- 0.9 ng ml-1, respectively) and thromboxane B2 (TxB2) (maximal release: 6.7 +/- 1.3 ng ml-1; 6.8 +/- 1.1 ng ml-1, respectively) from guinea-pig perfused lungs. ET-3 (2.5 nM) is also a potent releaser of PGI2 and TxB2 from the guinea-pig lungs (maximal release: PGI2: 2.4 +/- 1.0 ng ml-1; TxB2: 3.8 +/- 0.6 ng ml-1). Conversely, big-ET-3 (100 nM) does not increase basal release of eicosanoids. 4. Phosphoramidon (50 microM), a metalloprotease inhibitor, markedly reduced the eicosanoid releasing properties of big-ET-1 (n = 4, P less than 0.01) in guinea-pig perfused lungs without affecting the release stimulated by ET-1. 5. Our results suggest that big-ET-1 is converted to ET-1 via a phosphoramidon-sensitive endothelin converting enzyme (ECE) to release eicosanoids. The ECE is present in the guinea-pig pulmonary vasculature. Furthermore, our results suggest that the ECE activity is specific for big-ET-1 and may not convert big-ET-3 to its active metabolite, ET-3.