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In spontaneously hypertensive rat (SHR) aorta, prostacyclin is an endothelium-derived contracting factor contributing to the endothelial dysfunction. This study was designed to determine whether the impairment of the prostacyclin response is influenced by aging and whether such a dysfunction is observed in platelets. Isometric tension was measured in aortic rings, and aggregation was studied in platelet-rich plasma taken from 3-, 6-, and 15-too-old Wistar-Kyoto rats (WKY) and SHR. In aorta from 3- and 6-too-old WKY, prostacyclin and beraprost [prostacyclin receptor (IP) agonists] produced relaxations that were enhanced by Triplion (thromboxane-prostanoid receptor antagonist). In 15-mo-old WKY, the relaxations to beraprost were maintained, but not those to prostacyclin. In SHR aorta, prostacyclin or beraprost produced no or minor relaxations, which, in younger SHR, were enhanced by Triplion. In both strains, the relaxations were inhibited by CAY-10441 (IP receptor antagonist). The relaxations to forskolin and isoproterenol were reduced with aging. When compared with those of WKY, the relaxations to isoproterenol were reduced in 3- but not in 6- or 15-too-old SHR, whereas those to forskolin were consistently diminished at any given age. Whatever the age, prostacyclin and beraprost produced CAY-10441-sensitive inhibitions of ADPinduced platelet aggregation. Both agonists were more potent in SHR than in WKY. Therefore, in platelets from WKY and SHR, the IP receptor-dependent antiaggregant response is functional and maintained during aging. In aorta from WKY those responses are reduced by aging and, in SHR, are already compromised at 3 too. This dysfunction of the IP receptor is only partially explained by a general dysfunction of the adenylate cyclase pathway. smooth muscle; prostacyclin receptor; endothelium-derived contracting factors; endothelial dysfunction; spontaneously hypertensive rats; Wistar-Kyoto rats

Early manifestations of kidney disease occur in atherosclerosis and activation of TP (thromboxane [A.sub.2]) receptors is implicated in atherosclerotic, diabetes, and renal diseases. The purpose of the present study was to analyze, in isolated, perfused mouse kidneys, the participation of TP receptors in renal vasoconstrictions and vasodilatations. In kidneys, taken from wild-type C57BL6, apolipoprotein E-deficient (ApoE-KO) and diabetic ApoE-KO mice, changes in perfusion pressure were recorded. Constrictions to TP receptor ligands U 46619, arachidonic acid, [PGH.sub.2], and 8-iso-[PGF.sub.2[alpha]], but not those to angiotensin II, endothelin, or norepinephrine, were inhibited by the selective TP receptor antagonist Triplion (S 18886; 10 nM). Acetylcholine and prostacyclin evoked biphasic responses during methoxamine constrictions; the constrictor part was blocked by Triplion. In ApoE-KO mouse kidneys, compared with C57BL6, a specific decrease in norepinephrine response and no modification in dilator responses were observed. In diabetic ApoE-KO mouse kidneys, constrictions to U 46619 and those to 8-iso-[PGF.sub.2[alpha]] were significantly and selectively augmented, without modification in the expression of the TP receptor, and again without any significant change in vasodilator activity. Thus TP receptors are functional, and their activation is not involved in norepinephrine, endothelin, and angiotensin II vasoconstrictions but is implicated in the unusual vasoconstrictions to acetylcholine and prostacyclin. Increased responsiveness of TP receptors occurs in diabetic ApoE-KO mouse kidneys. Thus early changes in TP receptor-mediated vasoconstrictor activity may participate in the development of kidney disease in atherosclerosis and diabetes. vasoconstriction; atherosclerosis; diabetes; perfused mouse kidney

In canine coronary artery preparations, the proteinase-activated receptor-2 ([PAR.sub.2]) activating peptides ([PAR.sub.2]-APs) SLIGRL-[NH.sub.2] and 2-furoyl-LIGRLO-[NH.sub.2] caused both an endothelium-dependent relaxation and an endothelium-independent contraction. Relaxation was caused at peptide concentrations 10-fold lower than those causing a contractile response. Although trans-cinnamoyl-LIGRLO-[NH.sub.2], like other [PAR.sub.2]-APs, caused relaxation, it was inactive as a contractile agonist and instead antagonized the contractile response to SLIGRL-[NH.sup.2]. RT-PCR-based sequencing of canine [PAR.sup.2] revealed a cleavage/activation (indicated by underlines) sequence (SKGR/SLIGKTDSSLQITGKG) that is very similar to the human [PAR.sup.2] sequence (R/SLIGKV). As a synthetic peptide, the canine PAR-AP (SLIGKT-[NH.sub.2]) was a much less potent agonist than either SLIGRL-[NH.sub.2] or 2-furoyl-LIGRLO-[NH.sub.2], either in the coronary contractile assay or in a Madin-Darby canine kidney (MDCK) cell [PAR.sub.2] calcium signaling assay. In the MDCK signaling assay, the order of potencies was as follows: 2-furoyl-LIGRLO-[NH.sub.2] [much greater than] SLIGRL-[NH.sub.2] = trans-cinnamoyl-LIGRLO-[NH.sub.2] [much greater than] SLIGKT-[NH.sub.2], as expected for [PAR.sub.2] responses. In the coronary contractile assay, however, the order of potencies was very different: SLIGRL-[NH.sub.2] [much greater than] 2-furoyI-LIGRLO-[NH.sub.2] [much greater than] SLIGKT-[NH.sub.2], trans-cinnamoyl-LIGRLO-[NH.sub.2] = antagonist. Because of 1) the distinct agonist (relaxant) and antagonist (contractile) activity of trans-cinnamoyl-LIGRLO-[NH.sub.2] in the canine coronary contractile assays, 2) the different concentration ranges over which the peptides caused either relaxation or contraction in the same coronary preparation, and 3) the markedly distinct structure-activity profiles for the PAR-APs in the coronary contractile assay, compared with those for [PAR.sub.2]-mediated MDCK cell calcium signaling, we suggest that the canine coronary tissue possesses a receptor system for the PAR-APs that is distinct from [PAR.sub.2] itself. protease; vascular G protein-coupled receptor

The (pro)renin receptor (PRR) has recently been demonstrated to bind equally well renin and its precursor, prorenin, leading to a similar intracellular signaling independent of angiotensin II. In this study, we report that human embryonic kidney cells (HEK) exposed to renin or prorenin for 24 h in the presence of a blocking concentration of the angtiotensin-converting enzyme inhibitor perindoprilate increased superoxide anion production as measured by luminescence (lucigenin) and electron spin resonance spectroscopy (hydroxylamine radical transition). Also, both renin and prorenin increased Nox4 expression while Nox2, p47phox, and p67phox remained unchanged. In an investigation of the effects of renin and prorenin on fibrosis genes, it appeared that both proteins stimulated transforming growth factor-β (TGF-β), fibronectin, and plasm inogen activator inhibitor type 1 (PAl-1) expression and therefore participated to an overall switch toward a profibrotic state of the kidney cells. When the cells were transfected with a siRNA targeting the PRR, Nox4 expression was efficiently prevented as well as the increase in superoxide production, TGF-13, fibronectin, and PAl- 1. Finally, we demonstrated that transfection of the cells with a Nox4- specific small interfering (si) RNA also prevented fibrosis gene expression following treatment with renin or prorenin. The results demonstrate that renin and prorenin, through their specific membrane receptor and independently of angiotensin II, promote fibrosis gene expression via a Nox4-dependent mechanism. [ABSTRACT FROM AUTHOR]

Large-artery stiffening is a major risk factor in aging and hypertension. Elevated blood pressure (BP) and vascular wall properties participate in arterial stiffening; we aimed to evaluate their respective role by combining echo-tracking and the spontaneously hypertensive rats (SHR) treated with low doses of a nitric oxide synthase inhibitor, shown to have arterial stiffening. Normotensive [Wistar-Kyoto (WKY)], SHR, and SHR treated for 2 wk with N(G)-nitro-L-arginine methyl ester (SHRLN) were anesthetized; BP and distension (pulsatile displacement) of the aortic walls with the ArtLab echo-tracking device were measured. Stiffness index increased in SHRLN vs. SHR; compliance, distensibility, and the slopes and area of the distension-pressure loop curve decreased. The pulsatile distension and pressure waveforms were strongly altered in SHRLN. Maximal values were decreased and increased, respectively, and the waveform kinetics also differed. Thus the area under the curve adjusted to heart rate (AUC/ms) was calculated. Acute BP reductions were induced by diltiazem in SHR and SHRLN, to levels similar to those of WKY. In SHR, compliance, distensibility, stiffness index, and the ascending slope of the distension-pressure loop reached the values of WKY, whereas they were only partially improved in SHRLN. Aortic distension (maximal value and AUC/ms) and the area of the distension-pressure loop were improved in SHR, but not in SHRLN. These data confirm the aortic stiffening induced by nitric oxide reduction in SHR. They show that the ArtLab system analyzes aortic stiffness in rats, and that the aortic pulsatile distension waveform is a parameter strongly dependent on the vascular wall properties.