The hemodynamic and metabolic profiles of Zucker diabetic fatty rats treated with a single molecule triple vasopeptidase inhibitor, CGS 35601

CGS 35601 is a triple vasopeptidase inhibitor (VPI) of angiotensin converting enzyme (ACE), neutral endopeptidase (NEP), and endothelin (ET) converting enzyme-1 (ECE-1), with respective IC(50) values of 22, 2, and 55 nM. The aim of the present study was to establish the hemodynamic profile of Zucker diabetic fatty (Zdf)-Fatty rats, a high-fat diet gene-prone model developing spontaneous Type 2 diabetes (T2D) and the effects of CGS 35601. Male Zdf-Fatty (14 weeks, n = 17-23), Zdf-Lean (14 weeks, n = 8-10), and Wistar (14 weeks, n = 9-10) rats on distinct diets were implanted with a catheter in the left carotid and placed individually in a metabolic cage for 30 days. The hemodynamic profile and some metabolic biomarkers were assessed daily. After a 7-day stabilization period, the Zdf-Fatty rats were divided into two groups: Group 1, controls (n = 7-10) receiving vehicle-saline (250 microl/hr) and Group 2, (n = 10-13) receiving increasing doses of CGS 35601 (0.1, 1, and 5 mg/kg/day x 6 days each, intra-arterially) followed by a 5-day washout period. Mean arterial blood pressure (MABP) of young Zdf-Fatty rats was compared with age-matched Zdf-Lean and Wistar rats, which were found similar. MABP decreased by 5.9% (from baseline at 102 +/- 5 to 96 +/- 4 mmHg), 12.7% (to 89 +/- 6 mmHg) and 21.6% (to 80 +/- 4 mmHg), at 0.1, 1, and 5 mg/kg/day, respectively, in CGS 35601-treated Zdf-Fatty rats. Systolic and diastolic blood pressures were similarly reduced. The heart rate was not affected. Hyperglycemic status and insulin-resistance were not modulated by short-term treatment. CGS 35601 presented an excellent short-term safety profile. This novel molecule and class of VPI may be of interest for lowering vascular tone. Further long-term studies, once cardiovascular and renal complications have developed in this T2D rat model are warranted to define the efficacy of this class of VPI.

Heterozygous knock-Out of ET(B) receptors induces BQ-123-sensitive hypertension in the mouse

Homozygous knock-out of ET(A) or ET(B) receptor genes results in lethal developmental phenotypes in the mouse. Such deleterious phenotypes do not occur in heterozygous littermates. However, it remains to be determined whether mice partially defective in ET(A) or ET(B) receptors display significant alterations in their responses to exogenous or endogenous endothelin-1 (ET-1). Furthermore, the anesthetized ET(B) (+/-) knock-out mice showed a significantly higher mean arterial blood pressure than the ET(A) (+/-) knock-out or their wild-type littermates. The pressor response to ET-1 but not to a selective ET(B) agonist, IRL-1620, was significantly reduced in the ET(A) (+/-) knock-out mice. In ET(B) (+/-) knock-out mice, the pressor effect of IRL-1620 was more markedly altered than those induced by ET-1. In wild-type mice, both ET(A) and ET(B) receptors were found to be involved in the pressor effect of ET-1, as confirmed by the significant and specific antagonism induced by either BQ-123 (ET(A) antagonist) or BQ-788 (ET(B) antagonist). Also, ET(A)-selective or mixed ET(A)/ET(B)- but not ET(B)-selective antagonists reversed the hypertensive state of the ET(B) (+/-) knock-out mice to the level of wild-type littermates. Finally, radiolabeled ET-1 plasmatic clearance was altered in ET(B) (+/-) but not ET(A) (+/-) knock-out mice when compared with wild-type animals. Thus, heterozygous knock-out of ET(B) receptors results in a hypertensive state, suggesting an important physiological role for that particular receptorial entity in opposing the endogenous ET-1-dependent pressor effects in the mouse.

Contribution of endogenous endothelin-1 and endothelin-A-receptors to the hypertensive state of endothelin-B heterozygous (+/-) knockout mice

We observed that heterozygous knockout (+/-, KO) of either endothelin-A- (ET(A)) or -B- (ET(B)) receptors significantly reduced the pressor responses to systemically administered endothelin-1 (ET-1) in ET(A) or ET(B) (+/-) KO mice when compared to wild-type (WT) mice (data not shown). Also, we observed that basal mean arterial pressure (MAP) is significantly higher in ET(B) (+/-) (92.7 +/- 1.2 mmHg) (n = 53, p < 0.05) but not ET(A) (+/-) KO mice (70.6 +/- 1.8 mmHg) (n = 23) when compared to their anaesthetized WT littermates (70.1 +/- 0.7 mmHg) (n = 118). A 90 min treatment with either BQ-123 (10 mg/kg), an ET(A)-selective antagonist, or BQ-928 (10 mg/kg), a mixed ET(A)/ET(B) antagonist, administered intraperitoneally, significantly reduced basal MAP of ET(B) (+/-) KO mice almost to the level of their WT treated counterparts (94.9 +/- 4.9 mmHg) (n = 6) vs (+ BQ-123: 59.7 +/- 0.3 mmHg, n = 8); (+ BQ-928: 72.4 +/- 2.6 mmHg, n = 5). It is worthy of note that BQ-123 significantly reduced basal MAP in WT mice but to a lesser extent than in ET(B) (+/-) KO mice (69.6 +/- 2.3 mmHg, n = 8) vs (+ BQ-123: 57.3 +/- 1.4 mmHg, n = 8). In contrast, the ET(B)-selective antagonist, BQ-788 (10 mg/kg i.p.), had no significant effect on MAP even after 90 min of treatment (ET(B) (+/-) KO: (92.3 +/- 2.3 mmHg, n = 6) vs (+ BQ-788: 89.7 +/- 3.1 mmHg, n = 6); WT: (70.5 +/- 3.7 mmHg, n = 7) vs (+ BQ-788: 71.2 +/- 2.0 mmHg, n = 6). Therefore heterozygous KO of either ET(A)- or ET(B)-receptors significantly alters the phenotypic pressor properties of ET-1. We also suggest that there is less ET clearance in ET(B) (+/-) KO mice than in WT mice, which can explain the ET(A)-dependent hypertensive state of the former strain.

Pharmacology of endothelins in vascular circuits of normal or heterozygous endothelin-A or endothelin-B knockout transgenic mice

Endothelin-1 (ET-1; 0.001-1 nmol) and the ETB receptor agonist IRL-1620 (0.01-1 nmol) induced a dose-dependent vasoconstriction of the arterial and venous mesenteric circuits and of the kidney in normal mice. BQ-123 (10(-7) M) or BQ-788 (10(-7) M) abolished the vasoconstriction induced by ET-1 in the arterial mesenteric and renal vasculatures without affecting that of norepinephrine (NE). In the venous mesenteric vasculature, only BQ-123 reduced the response to ET-1 but not to NE. In other experiments we compared the mesenteric and renal vascular reactivities to ET-1 and IRL-1620 in ETA or ETB heterozygous knockout mice with those of the wild-type strain. We observed a significant reduction in vascular reactivity to ET-1 but not to IRL-1620 in the arterial mesenteric and renal but not the venous mesenteric circuits of ETA knockout mice. In contrast, there was a significant reduction in vascular reactivity to ET-1 and IRL-1620 in the arterial mesenteric and renal circuits of ETB knockout mice. In the venous mesenteric vasculature, only the vasoconstriction induced by IRL-1620 was significantly reduced in the same ETB knockout strain. Our results suggest that, in the mouse, arterial mesenteric and renal vasoconstriction to ET-1 is mediated by both subtypes of ET receptors, whereas venous mesenteric vasoconstriction appears to be mediated uniquely by the ETA receptor subtype. Knockout of only one allele of the ETA or ETB gene appears to be sufficient for reduction of the ET-1 or IRL-1620 vasoconstrictor effects in the mesenteric and renal vascular beds of the mouse.

[Role of neutral endopeptidases in capillary dysfunctions of diabetic origin in rats]

Among numerous complications associated with diabetes, the alterations of the normal properties of various microcirculation circuits lead to important dysfunctions which may contribute to target organ damage. As the endothelium plays a crucial role in the microcirculatory circuits, it is suggested that diabetes may influence both the physical and endocrine properties of that cell layer. In 1995, we reported an important increase in plasma extravasation in a model of diabetes in rats treated with streptozotocin. The increase of plasma extravasation was particularly significant in the pulmonary, skin and splanchnic areas. In that particular study, it was of interest that inhibitors of neutral endopeptidases, such as thiorphan, phosphoramidon and SQ 28,603 (specific inhibitor of the recombinant neutral endopeptidases2) corrected almost completely the increase of plasma extravasation induced by diabetes when compared with control rats. It is also worthy of note that the three above-mentioned inhibitors failed to normalize in any case the hyperglycaemia associated with the diabetes in these animals. The present document is a summary synthesis of the putative role of neutral endopeptidases and of the beneficial effects of the inhibitors of these enzymes in diabetes-induced plasma extravasation in the rat.

Pharmacology of kinins in the arterial and venous mesenteric bed of normal and B2 knockout transgenic mice

We have tested the vasoactive effects of kinins in addition to various other endothelium-dependent or independent agonists in the arterial and venous perfused mesenteric circuits of the mouse. Bradykinin (0.1 pmol-100 nmol), but not des-Arg9-bradykinin (10 nmol) induced a dose-dependent vasodilation of the precontracted arterial and venous mesenteric vasculature of the mouse. Furthermore, acetylcholine (2.5 nmol) also induced a marked arterial vasodilation but was without effect on the venous side. Other endothelium-dependent vasodilators, such as platelet-activating factor (PAF) (1 nmol), tachykinin NK1 selective agonist ([Sar9,Met(O2)(l1) ]substance P) (0.5 nmol) and adenosine diphosphate (5 nmol), were without effect on either side of the mesenteric bed of the mouse. The bradykinin B2 receptor selective antagonist (HOE 140) abolished the arterial and venous vasodilation induced by bradykinin without affecting that of acetylcholine or sodium nitroprusside. In addition, the bradykinin B1 receptor antagonist des-Arg9-[Leu8]bradykinin was without effect on the responses induced by bradykinin. A nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) markedly reduced, whereas removal of the endothelium with 3-[3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS) abolished dilatation to bradykinin and acetylcholine (arterial side only) without affecting that induced by sodium nitroprusside in the mouse arterial and venous mesenteric circuits. In the same two circuits of transgenic B2 knockout mice, the vasodilatory responses to bradykinin were absent, whereas the arterial circuit still responded to acetylcholine by a L-NAME-sensitive vasodilation. Our results suggest the exclusive contribution of B2 receptors located on the endothelium in the vasodilatory effects of bradykinin in the arterial and venous mesenteric circuits of the mouse.

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.

The selection of needs indicators for regional resource allocation in the fields of health and social services in Québec

In Québec, recent political statements have strengthened the necessity to allocate resources according to regional population needs. A regional-provincial working group was set up to propose needs indicators in 8 different fields-or client-oriented programs-which subdivide the entire spectrum of health and social services in Québec. These programs include physical health, mental health, public health, functionally impaired elderly people, physical deficiency, intellectual deficiency, alcoholism and drug abuse and problems (abuse, neglect, delinquency) among young people and their families. The following paper summarizes the main proposals of the working group. Some comments are made on the definition of client-oriented programs, basic concepts, research questions and methodological approaches. Concrete examples are given in order to illustrate the type of data and methods used. Furthermore, the indicators selected for resource allocation (in each of the 8 client-oriented programs) are presented on a regional basis (n = 18) and introduced in a principal component analysis. Their variations are discussed and recommendations to facilitate their use and promote their development are made. Finally, the actual utilization of these indicators is reported.

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.

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.