Ischemic preconditioning changes the pattern of coronary reactive hyperemia regardless of mitochondrial ATP-sensitive K(+) channel blockade

Ischemic preconditioning increases the velocity of vasodilatation and reduces the total hyperemic flow (THF) of a subsequent coronary reactive hyperemia (CRH). The increase in the velocity of vasodilatation has been shown to depend on an up-regulation of the endothelial release of nitric oxide, while the reduction of THF is attributed to an adenosine A(1) receptor-mediated mechanism. We investigated whether the changes in CRH induced by preconditioning ischemia (PI) can still be obtained after blockade of mitochondrial ATP-sensitive K(+) channels by sodium 5-hydroxydecanoate (5-HD), and whether the blockade per se affects the pattern of CRH.In anesthetized goats, flow was recorded from the left circumflex coronary artery (LCCA). CRH was obtained with the occlusion of LCCA for 15 s. PI was obtained by 2 cycles of 2.5 min of LCCA occlusion with a 5 min interval of reperfusion between the two occlusions. CRH was studied before and after i.v. administration of 5-HD (20 mg/kg), as well as in the presence of 5-HD after PI. Following 5-HD, the pattern of CRH remained unchanged. After 5-HD and PI, velocity of vasodilatation and total hyperemic flow of CRH showed the same changes as in previous studies after PI alone. It was concluded that the blockade of mitochondrial ATP-sensitive K(+) channels, which is reported to prevent myocardial protection, does not affect CRH and does not prevent PI from increasing the velocity of vasodilatation and reducing THF. These results demonstrate that the changes induced in CRH by preconditioning are independent of the opening of the mitochondrial ATP-sensitive K(+) channels.     

阿托伐他汀改善冠心病患者血管内皮功能的临床研究

目的:观察短期阿托伐他汀治疗对高胆固醇血症的冠心病患者血管内皮功能的影响。方法:78例高胆固醇血症患者每日口服阿托伐他汀共8周,服药前后测量患者血清的总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)和氧化低密度脂蛋白(ox-LDL)以及NO值,并用彩色多普勒超声测定反应性充血时肱动脉内径的变化。结果:高胆固醇血症患者经阿托伐他汀8周治疗后,血清的TC、TG、LDL-C和ox-LDL明显下降,血清的HDL-C以及NO值明显增加,反应性充血时肱动脉内径扩张程度明显增加,这些与治疗前相比有明显差异。结论:阿托伐他汀治疗能使高胆固醇血症的冠心病患者血脂改变,NO值增加,血管内皮功能改善。     

The potent vasodilator ethyl nitrite is formed upon reaction of nitrite and ethanol under gastric conditions

By acting as a bioreactor, affording chemical and mechanical conditions for the reaction between dietary components, the stomach may be a source of new bioactive molecules. Using gas chromatography-mass spectrometry we here demonstrate that, under acidic gastric conditions, ethyl nitrite is formed in microM concentrations from the reaction of red wine or distilled alcoholic drinks with physiological amounts of nitrite. Rat femoral artery rings and gastric fundus strips dose-dependently relaxed upon exposure to nitrite:ethanol mixtures. In contrast, when administered separately in the same dose ranges, nitrite evoked only minor vasorelaxation while ethanol actually caused a slight vasoconstriction. Mechanistically, the relaxation effect was assigned to generation of nitric oxide (*NO) as supported by direct demonstration of *NO release from ethyl nitrite and the absence of relaxation in the presence of the soluble guanylyl cyclase inhibitor, ODQ. In conclusion, these results suggest that ethanol in alcoholic drinks interacts with salivary-derived nitrite in the acidic stomach leading to the production of the potent smooth muscle relaxant ethyl nitrite. These findings reveal an alternative chemical reaction pathway for dietary nitrate and nitrite with possible impact on gastric physiology and pathophysiology.     

Ruffini Mechanoreceptors in Isolated Joint Capsule: Responses Correlated with Strain Energy Density

Mechanoreceptive afferents innervating the posterior capsule of the cat knee joint were recorded in a preparation of isolated capsule. The purpose of the experiments was to identify mechanical states in the capsule that were associated with afferent discharge. The capsule was excised from the knee with its bone attachments intact, so that the geometry of the capsule could be reproduced in vitro. The capsule was deformed, and measurements were made of stresses and strains in the plane of the capsule. Afferent discharge was correlated with each of the components of plane stress, plane strain, and strain energy density (SED). SED, the stored elastic energy at the receptor location, was the only mechanical variable that was consistently positively correlated with afferent discharge. A model of the Ruffini-type receptor is presented that accounts for the sensitivity to SED.     

3,4-Dihydroxyphenethyl nitrate with nitric oxide releasing,antioxidant, hypoglycemic and hypolipidemic effects

Nitric oxide (NO) dysfunction, oxidative stress, and dyslipidemia are main risk factors associated with the pathophysiology of diabetic complications. In this study, 3,4-dihydroxyphenethyl nitrate (HT-ONO₂) was designed, synthesized and evaluated, which incorporated hydroxytyrosol (HT) and nitrate. HT-ONO₂ significantly exhibited hypoglycemic activity after oral administration to diabetic mice induced by streptozocin (STZ). HT-ONO₂ also potently decreased plasma triglyceride (TG), total cholesterol (TC) in hyperlipidemia mice induced by Triton WR 1339. Meanwhile, HT-ONO₂ displayed NO-releasing and antioxidant activity both in diabetic and hyperlipidemia mice and in vitro. Moreover, HT-ONO₂ shown definite vasodilation and α-glucosidase inhibition activity in vitro. The results suggested that the hybrid hydroxytyrosol-based nitrate with NO supplement, antioxidant, hypoglycemia and hypolipidemia provided a potential multi-target agent to ameliorate the diabetes mellitus and its complications.     

Cholinergic Dilatation and Constriction of Feline Cerebral Blood Vessels Are Mediated by Stimulation of Phosphoinositide Metabolism via Two Different Muscarinic Receptor Subtypes

Abstract: The muscarinic receptors involved in phosphoinositide (PI) hydrolysis have been pharmacologically characterized in cat cerebral blood vessels. Carbachol elicited a concentration-dependent increase in inositol phosphate accumulation [inositol monophosphate, bisphosphate, trisphosphate (IP₃) and tetrakisphosphate] in both major cerebral arteries and small pial vessels, which reached 140–280% of baseline at 10^?3M carbachol (referred to as maximal effect). However, the inositol phosphate accumulation response was found to be biphasic with a submaximal effect (30–50% of the maximal stimulation) obtained at low carbachol concentrations (<10^?5M). Endothelial denudation induced a virtual disappearance of the submaximal PI response without affecting that elicited by high concentrations of carbachol. The pharmacology of the two carbachol-induced PI responses was investigated by comparing the potency of selected muscarinic antagonists to block the IP₃ accumulation induced by 10^?7M (endothelium-dependent submaximal effect) and 10^?4M (endothelium-independent near-maximal effect) carbachol. In both major arteries and pial vessels, the activation of IP₃ production by 10^?4M carbachol was similarly inhibited by muscarinic antagonists with the following averaged rank order of potency (in -log IC₅₀): 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; 8.65) > pirenzepine (8.28) > 6-chloro-5,10-dihydro-5-[(1-methyl-4-piperidinyl)acetyl]-11H-dibenzo[b,e][1,4]diazepine-11-one (UH-AH 371; 7.87) > 11-[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5,-11-dihydro-6H-pyridol[2,3-b][1,4]benzodiazepine-6-one (AF-DX 116; 6.62), a pharmacological profile compatible with an M₁ receptor subtype. In contrast, the submaximal stimulation of the PI metabolism elicited by 10^?7M carbachol in major arteries was blocked by the same antagonists with the following order of potency (in -log IC₅₀): 4-DAMP (8.38) > pirenzepine (7.25) > UH-AH 371 (6.25) > AF-DX 116 (5.72), which was reminiscent of an M₃ pharmacological profile. These findings indicate that stimulation of cerebrovascular muscarinic receptors is accompanied by PI hydrolysis via two distinct receptors, most probably the M₁ and M₃ subtypes that have been associated with constriction and dilatation, respectively, of cat cerebral arteries. Furthermore, these results provide strong evidence for an endothelial localization of the M₃ dilatatory receptors within the vessel wall.     

Identification of P1 and P2 purinoceptors in the aorta of the lizard (Agama sp.)

In the isolated Agama lizard aorta, acetylcholine (ACh; 3 nM-100 microM), noradrenaline (NA; 30 nM-0.3 mM), adrenaline (Adr; 30 nM-300 microM), adenosine 5'-triphosphate (ATP; 30 nM-1 mM), alpha,beta-methylene ATP (alpha,beta-meATP; 10 nM-10 microM), beta,gamma-methylene ATP (beta,gamma-meATP; 0.1-300 microM), 2-methylthio ATP (2-meSATP; 30 nM-30 microM) and high concentrations of uridine triphosphate (UTP; 1 microM-1 mM), all produced constriction. The P2 receptor antagonists pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS; 30 microM), suramin (0.1 mM) and Reactive blue 2 (30 microM) all raised vascular tone and could not be utilized and the antagonist 2'-O-(trinitrophenyl) ATP (TNP-ATP; 0.1 microM) had no effect on responses to the ATP analogues. alpha,beta-MeATP (3 microMx3) desensitised responses to alpha,beta-meATP (10 microM) and beta,gamma-meATP (0.3 mM), but not to ATP (0.3 mM) or 2-meSATP (30 microM). On pre-constricted aorta (EC50 concentration of either ACh or Adr), adenosine (1 microM-1 mM), the A1-selective agonist N6-cyclopentyl adenosine (CPA; 1-300 microM) [but not the A2- and A3-selective agonists CGS 21680 and IB-MECA respectively (both up to 30 microM)] and sodium nitroprusside (10 nM-100 microM) produced vasodilatation. Adenosine vasodilatation was antagonised by 8-p-sulfophenyl-theophylline (8-pSPT; 30 microM) but not by N(omega)-nitro-L-arginine methyl ester (L-NAME; 0.1 mM). ATP (up to 0.3 mM), 2-meSATP (up to 10 microM) and UTP (up to 1 mM) were not vasodilators. In summary, A1 receptors mediating relaxation and excitatory P2X1 receptors were identified in the smooth muscle of the lizard aorta. However, in contrast to mammalian aorta, P2Y receptors on endothelial cells mediating vasodilatation via nitric oxide do not appear to be present.     

Increase on the coronary flow induced by dioclein in isolated rat heart

In the present work the effect of dioclein, a new flavonoid from Dioclea grandiflora, was investigated in rat hearts. The experiments were performed using the classic method of Langendorff, where flow, inotropic, chronotropic and electric parameters were analyzed. Bolus administration of Dioclein (1-100 microg) induced a sustained and dose-dependent increase in coronary flow with no modification in inotropic, chronotropic and electrical parameters. The duration of increase in coronary flow induced by dioclein (10 microg) was approximately 4-fold higher than that observed in the presence of sodium nitroprusside (NPS; 10 microg). Besides, the effect of dioclein measured as the area-under-the-curve was approximately 4.5-folds higher than that observed with NPS. Pre-treatment with L-NAME (100 microM) and indomethacin (10 microM) alone did not modify the effect of dioclein (10 microg), suggesting that nitric oxide (NO) and cyclooxygenase-derived factors were not involved. However, association of L-NAME plus indomethacin inhibited the duration of the effect of dioclein (10 microg) without changing its increase in the coronary flow. Furthermore, the absence of alteration in inotropism and chronotropism of the heart associated with its coronary effect suggest that dioclein could be an interesting lead compound for the development of drugs for the treatment coronary heart diseases.     

Lysophosphatidylcholine alters vascular tone in rat aorta by suppressing endothelial [Ca<Superscript>2+</Superscript>]<Subscript>i</Subscript> signaling

The detailed mechanism of how lysophosphatidylcholine (LPC) suppresses endothelium-dependent vasodilatation is unclear at present. We investigated the effects of LPC on endothelial intracellular calcium (EC [Ca(2+)](i)) signaling and vascular tone simultaneously using a new technique we developed. Fura-2-labeled rat aortic specimens were mounted in a tissue flow chamber and precontracted with phenylephrine (5 x 10(-8) M). Under either basal or agonist-stimulated conditions, the EC [Ca(2+)](i) level was calculated from fura 2 fluorescence ratio images, and the vascular tone was estimated by measuring the relative displacement of the fluorescence images. Although both acetylcholine (ACh)-induced EC [Ca(2+)](i) elevation and the concomitant vasorelaxation were partially suppressed in specimens pretreated with LPC (20 microM), the quantitative relationship between EC [Ca(2+)](i) elevation and the corresponding vasorelaxation was unaffected. A high concentration of LPC (40 microM) completely eliminated ACh-evoked [Ca(2+)](i) elevation and vasodilatation. It has been reported that exposing vascular tissue to a calcium-free buffer causes a reduction in the EC [Ca(2+)](i) level and the accompanying vasoconstriction. Pretreatment with 20 microM LPC reduced the basal EC [Ca(2+)](i) level and abolished the calcium-free solution-induced EC [Ca(2+)](i) reduction and vasoconstriction. We conclude that LPC impairs endothelium-dependent vasorelaxation mainly by reducing the basal EC [Ca(2+)](i) level and suppressing agonist-evoked EC [Ca(2+)](i) signaling.     

Human heart mitochondria do not produce physiologically relevant quantities of nitric oxide

Previous studies raised the possibility that nitric oxide synthase is present in heart mitochondria (mtNOS) and the existence of such an enzyme became generally accepted. However, original experimental evidence is rather scarce and positive identification of the enzyme is lacking. We aimed to detect an NOS protein in human and mouse heart mitochondria and to measure the level of NO released from the organelles. Western blotting with 7 different anti-NOS antibodies failed to detect a NOS-like protein in mitochondria. Immunoprecipitation or substrate-affinity purification of the samples concentrated NOS in control preparations but not in mitochondria. Release of NO from live respiring human mitochondria was below 2 ppb after 45 min of incubation. In a bioassay system, mitochondrial suspension failed to cause vasodilation of human mammary artery segments. These results indicate that mitochondria do not produce physiologically relevant quantities of NO in the heart and are unlikely to have any physiological importance as NO donors, nor do they contain a recognizable mtNOS enzyme.