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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

Atherosclerosis is associated with alterations in nitric oxide (NO)/ cGMP signaling. In early stages of the disease, inflammatory and possibly other cells produce reactive oxygen species that scavenge vasoprotective NO. In addition to the oxidative stress, expression and activity of enzymes downstream to NO formation may also be affected. Here, we show in the aortas of chronically hypercholesterolemic rabbits (a model of late-stage atherosclerosis), both subunits and specific activity of the NO receptor soluble guanylyl cyclase (sGC) were significantly reduced, whereas overall NO synthase activity was unaffected. These changes were most prominent in the neointimal layer, wherein cGMP-dependent protein kinase I (cGK) levels also were reduced. Additionally, a protein ([p38.sup.nt]) that was constitutively tyrosine-nitrated was detected, and its expression was significantly reduced in atherosclerotic aorta. Phosphorylation of the cGK substrate vasodilator-stimulated phosphoprotein (VASP) at Ser-239, an established biochemical endpoint of NO/cGMP signaling, also was reduced. Thus, late-stage atherosclerosis is associated not only with enhanced NO breakdown but also with altered NO reception and cGMP signaling. Preferential down-regulation in neointima suggests a direct connection of these changes to neointimal proliferation and vascular dysfunction and provides a rationale for future pharmacotherapy using classical and novel sGC activators. hypercolesterolemia | soluble guanylyl cyclase | vasodilator-stimulated phosphoprotein | cGMP-dependent protein kinase