Megathrust earthquake drives drastic organic carbon supply to the hadal trench.

The giant 2011 Tohoku-oki earthquake has been inferred to remobilise fine-grained, young surface sediment enriched in organic matter from the slope into the >7 km deep Japan Trench. Yet, this hypothesis and assessment of its significance for the carbon cycle has been hindered by limited data density and resolution in the hadal zone. Here we combine new high-resolution bathymetry data with sub-bottom profiler images and sediment cores taken during 2012-2016 in order to map for the first time the spatial extent of the earthquake-triggered event deposit along the hadal Japan Trench. We quantify a sediment volume of ~0.2 km3 deposited from spatially-widespread remobilisation of young surficial seafloor slope sediments triggered by the 2011 earthquake and its aftershock sequence. The mapped volume and organic carbon content in sediment cores encompassing the 2011 event reveals that this single tectonic event delivered >1 Tg of organic carbon to the hadal trench. This carbon supply is comparable to high carbon fluxes described for other Earth system processes, shedding new light on the impact of large earthquakes on long-term carbon cycling in the deep-sea.

Role of kinins in the pathophysiology of myocardial ischemia. In vitro and in vivo studies.

In ischemia, the heart generates and releases kinins as mediators that seem to have cardioprotective actions. Kinin-generating pathways are present in the heart. Kininogen, kininogenases, kinins, and B2 kinin receptors can be measured in cardiac tissue. Kinins are released under conditions of ischemia. In anesthetized rats and dogs with coronary artery ligation and in human patients with myocardial infarction, kinin plasma levels are increased. In isolated rat hearts, the outflow of kinins is enhanced during ischemia but markedly attenuated after deendothelialization, pointing to the coronary vascular endothelium as the main possible source. Kinins administered locally exert beneficial cardiac effects. In isolated rat hearts with ischemia-reperfusion injuries, perfusion with bradykinin (BK) reduces the duration and incidence of ventricular fibrillation, improves cardiodynamics, reduces release of cytosolic enzymes, and preserves energy-rich phosphates and glycogen stores. In anesthetized animals, intracoronary BK is followed by comparable beneficial changes and limits infarct size. Inhibition of breakdown of BK and related peptides induces beneficial cardiac effects. Treatment with ACE inhibitors such as ramipril increases cardiac kinin levels and reduces post-ischemic reperfusion injuries in isolated rat hearts and infarct size in anesthetized animals. The importance of an intact endothelium that continuously generates kinins is supported by observations that basal and ramipril-induced release of kinins and PGI2 is markedly reduced after deendothelialization of isolated hearts. Blockade of B2 kinin receptors increases ischemia-induced effects. Endothelial formation of NO and PGI2 by ACE inhibition is prevented by the specific B2 kinin receptor antagonist icatibant. In isolated hearts, ischemia-reperfusion injuries deteriorate with icatibant, which also abolishes the cardioprotective effects of ACE inhibitors and of exogenous BK. Infarct size reduction by ACE inhibitors and by BK in anesthetized animals is reversed by icatibant. Kinins contribute to the cardioprotective effects associated with ischemic preconditioning because preconditioning or BK-induced antiarrhythmic and infarct size-limiting effects are attenuated by icatibant. In conclusion, kinins may act as mediators of endogenous cardioprotective mechanisms. Kinins are generated and released during ischemia, with subsequent formation of PGI2 and NO probably derived mainly from the coronary vascular endothelium. Their cardioprotective profile resembles that of ACE inhibitors.

Vasodilator dysfunction in aged spontaneously hypertensive rats: changes in NO synthase III and soluble guanylyl cyclase expression, and in superoxide anion production.

OBJECTIVE/METHODS: Genetic hypertension is associated with an apparent endothelial dysfunction and impaired endothelium-dependent vasodilatation in response to increased flow and receptor-dependent agonists. However, the link between impaired vasodilatation and nitric oxide (NO) synthase expression is still unclear. In the present study, dilator responses were determined in the aorta and coronary circulation of 16 month old spontaneously hypertensive (SHR) and Wistar Kyoto rats (WKY). Changes in vascular reactivity were compared with alterations in superoxide anion production as well as endothelial NO synthase (NOS III) and soluble guanylyl cyclase expression. RESULTS: In the isolated perfused heart both the bradykinin- and sodium nitroprusside-induced vasodilator responses were attenuated in SHR compared to WKY. Western blot analysis revealed a parallel reduction in NOS III expression in coronary microvascular endothelial cells from SHR. Superoxide anion production in aortae from SHR was markedly elevated over that of aortae from WKY, and was almost completely abolished by pretreatment with superoxide dismutase. Superoxide dismutase induced similar relaxations in phenylephrine-preconstricted aortic rings from both SHR and WKY, but failed to restore the attenuated acetylcholine- and sodium nitroprusside-induced relaxations in SHR. No difference in NOS III expression was detected in the aortae from either strain whereas soluble guanylyl cyclase expression was markedly decreased in SHR. CONCLUSIONS: These results demonstrate that NOS III expression in different tissues is differentially affected by hypertension. Moreover, although an elevated superoxide anion production is apparent in the aorta, a reduced soluble guanylyl cyclase expression appears to account for the observed vasodilator dysfunction in SHR.

Ramiprilat enhances endothelial autacoid formation by inhibiting breakdown of endothelium-derived bradykinin.

We studied whether inhibition of angiotensin converting enzyme stimulates the formation of nitric oxide and prostacyclin in cultured human and bovine endothelial cells by an enhanced accumulation of endothelium-derived bradykinin. Nitric oxide formation was assessed in terms of intracellular cyclic GMP accumulation, prostacyclin release by a specific radioimmunoassay. Inhibition of angiotensin converting enzyme by ramiprilat dose- and time-dependently increased the formation of nitric oxide and prostacyclin. These increases, peaking within 10 minutes, were maintained for at least 60 minutes. The ramiprilat-induced cyclic GMP increase was completely abolished by the stereospecific inhibitor of nitric oxide synthase, NG-nitro-L-arginine. The B2-kinin receptor antagonist, Hoe 140 (0.1 microM), markedly attenuated the cyclic GMP accumulation and abolished the increase in prostacyclin release. The supernatant of endothelial cells, incubated with ramiprilat (0.3 microM) for 15 minutes, elicited a significant nitric oxide release (as assessed by a guanylyl cyclase assay) in untreated endothelial cells used as detector tissue. Preincubation of the detector cells with Hoe 140 completely abolished this nitric oxide release. These data indicate that cultured endothelial cells from different species are capable of producing and releasing bradykinin into the extracellular space in amounts that lead to a sustained stimulation of nitric oxide and prostacyclin formation, provided that bradykinin degradation is prevented by angiotensin converting enzyme inhibition. Thus, the protective effect of angiotensin converting enzyme inhibitors observed on endothelial vasomotor function in hypertension may be explained by the local accumulation of endothelium-derived bradykinin that acts in an autocrine and paracrine manner as potent stimulus for endothelial autacoid formation.

Angiotensin-converting enzyme inhibition alters nitric oxide and superoxide release in normotensive and hypertensive rats.

Young (approximately 1 month old) male normotensive Wistar-Kyoto rats (n=26) and spontaneously hypertensive rats (n=38) were randomized into three groups treated via drinking water for approximately 2 years with, respectively, placebo, low doses, or high doses of an angiotensin-converting enzyme inhibitor, ramipril (10 microg x kg[-1] x d[-1], non-blood pressure-lowering dose, or 1 mg x kg[-1] x d[-1], blood pressure-lowering dose). Relative to placebo treatment in each respective rat strain, both ramipril dosages increased endothelial constitutive nitric oxide synthase expression (Western blot) and resultant synthesis of nitric oxide (porphyrinic sensor) in freshly excised carotids and thoracic aortas, respectively. Paradoxically, this activity was associated with an increased/decreased superoxide accumulation (chemiluminescence) in freshly excised aortas from 24-/22-month-old normotensive/hypertensive rats. In normotensive rats, relative to placebo treatment, the threefold increase in superoxide accumulation with antihypertensive ramipril treatment is most likely from the >300% increase in endothelial constitutive nitric oxide synthase expression (some of which may be disarranged by local insufficiencies in L-arginine or tetrahydrobiopterin). In hypertensive rats, relative to placebo treatment, the 35% increase in nitric oxide availability by long-term antihypertensive ramipril treatment may contribute to the preservation of the endothelium and prevent its dysfunction by inhibiting superoxide production. Increased nitric oxide production with concomitant decreased superoxide accumulation (approximately one third of placebo levels) correlates positively with the previously reported +40% life span extension for rats with genetic hypertension that were treated with antihypertensive doses of ramipril.

Long-term angiotensin II type 1 receptor blockade with fonsartan doubles lifespan of hypertensive rats.

In this study, we investigated the outcome of lifelong treatment with the angiotensin II type 1 receptor (AT(1)) blocker fonsartan (HR 720) in young stroke-prone spontaneously hypertensive rats (SHR-SP). In addition to the primary end point, lifespan, and to determine the mechanisms involved in the treatment-induced effects, parameters such as left ventricular hypertrophy, cardiac function/metabolism, endothelial function, and the expression/activity of endothelial nitric oxide synthase and of angiotensin-converting enzyme (ACE) were also investigated. Ninety 1-month-old SHR-SP were allotted to 2 groups and treated via drinking water with an antihypertensive dose of fonsartan (10 mg. kg(-1). d(-1)) or placebo. Fonsartan doubled the lifespan to 30 months in SHR-SP, which was comparable to the lifespan of normotensive Wistar-Kyoto rats. After 15 months, a time when approximately 80% of the placebo group had died, left ventricular hypertrophy was completely prevented in fonsartan-treated animals. Furthermore, cardiac function and metabolism as well as endothelial function were significantly improved. These effects were correlated with increased endothelial nitric oxide synthase expression in the heart and carotid artery and with markedly decreased tissue ACE expression/activities. Lifespan extension and cardiovascular protection by long-term AT(1) blockade with fonsartan led to similar beneficial effects, as observed with long-term ACE inhibition.

Cardiac and vascular effects of long-term losartan treatment in stroke-prone spontaneously hypertensive rats.

In previous studies in stroke-prone spontaneously hypertensive rats (SHRSP), we demonstrated that early-onset, long-term angiotensin-converting enzyme inhibitor treatment improved cardiac function and metabolism and increased aortic cGMP content even at sub-antihypertensive doses. These effects could be prevented by bradykinin type 2 (B2) receptor blockade with icatibant. In the present study, we studied the effects of long-term oral treatment with the angiotensin type 1 (AT1) receptor antagonist losartan (30 mg/kg per day) on functional and biochemical parameters of the heart and on cGMP content in the aorta in SHRSP treated prenatally and subsequently up to the age of 20 weeks. Losartan prevented the development of hypertension and left ventricular hypertrophy. Cardiac function measured ex vivo in isolated perfused hearts was improved, as demonstrated by significant increases in left ventricular pressure (22.4%), differentiated left ventricular pressure (dP/dtmax) (35.1%), and coronary flow (38%). The release of the intracellular enzymes lactate dehydrogenase and creatine kinase and of lactate into the coronary effluent was reduced by 46.4%, 47.2%, and 63.6%, respectively. In myocardial tissue, the concentrations of glycogen and the energy-rich phosphates ATP and creatine phosphate were increased by 43.2%, 33.1%, and 42.4%, respectively, whereas lactate was decreased by 57.0%. The aortic tissue content of cGMP was increased fivefold. Our results demonstrate that chronic blockade of AT1 receptors with losartan improved cardiac function and metabolism and increased aortic cGMP content in SHRSP to an extent similar to that observed previously after long-term angiotensin-converting enzyme inhibitor treatment at a comparably antihypertensive dose. Prevention of hypertension and cardiac hypertrophy as well as stimulation of non-AT1 receptors are discussed to explain the cardiac and vascular actions of losartan.

Endothelial dysfunction coincides with an enhanced nitric oxide synthase expression and superoxide anion production.

We investigated the effects of aortic banding-induced hypertension on the endothelium-dependent vasodilator responses in the aorta and coronary circulation of Sprague-Dawley rats. We studied the influence of hypertension on the endothelial nitric oxide synthase (NOS III) expression, assessed by Western blot and reverse transcription-polymerase chain reactions experiments, and on the superoxide anion (O2-) production. Two weeks after aortic banding, the endothelium-dependent relaxations were not altered. At this time, the expression of NOS III in the aorta and in confluent coronary microvascular endothelial cells (RCMECs) exhibited no marked changes, whereas O2- production was enhanced 1.9-fold in aortas from aortic-banded rats. Six weeks after aortic banding, the endothelium-dependent dilations were markedly impaired in the heart (50% decrease) and aorta (35% decrease). Analysis of NOS III protein and mRNA levels revealed marked increases in both aortas and confluent RCMECs (2.6- to 4-fold) from aortic-banded compared with sham-operated rats. There was no further increase in O2production in both the aorta and confluent RCMECs from aortic-banded rats. An enhanced nitrotyrosine protein level was also detected in the aorta from 6-week aortic-banded rats. These findings indicate that in hypertension induced by aortic banding, an enhanced O2- production alone is not sufficient to produce endothelial dysfunction. Endothelial vasodilator hyporesponsiveness was observed only when NOS III expression and O2- production were increased and was associated with the appearance of enhanced nitrotyrosine residues. This would suggest that the development of endothelial dysfunction is linked to an overproduction of not one, but two, endothelium-derived radicals that might lead to the formation of peroxynitrite.

Late treatment with ramipril increases survival in old spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) begin to die from cardiovascular complications at approximately 15 months of age. We tested whether chronic ACE-inhibitor treatment would extend the lifespan of such old animals. We also studied cardiac hypertrophy and function, endothelial function and expression, and activity of NO synthase (eNOS). One hundred 15-month-old SHR were randomized into 3 groups, control (n=10), placebo-treated (n=45), and ramipril-treated with an antihypertensive dose of 1 mg. kg(-1). d(-1) in drinking water (n=45). Ex vivo experiments were performed after 15 months (control) and 21 months, when approximately 80% of the placebo group had died. Late treatment with ramipril significantly extended lifespan of the animals from 21 to 30 months. Fully established cardiac hypertrophy, observed in placebo-treated animals and in controls, was significantly reversed by ramipril treatment. In isolated working hearts, a significantly improved function associated with increased cardiac eNOS expression was seen versus placebo and control hearts. Endothelial dysfunction in isolated aortic rings from control and placebo-treated SHR was significantly improved by ACE inhibition and associated with enhanced NO release. Late treatment of SHR with the ACE inhibitor ramipril extended lifespan from 21 to 30 months, which is comparable to the lifespan of untreated normotensive Wistar-Kyoto rats. This lifespan extension, probably due to blood pressure reduction, correlated with increased eNOS expression and activity followed by a regression of left ventricular hypertrophy and cardiac and vascular dysfunction.

Long-term low-dose angiotensin converting enzyme inhibitor treatment increases vascular cyclic guanosine 3',5'-monophosphate.

We investigated functional changes in aortic preparations of spontaneously hypertensive rats treated in utero and subsequently up to 20 weeks of age with the angiotensin converting enzyme (ACE) inhibitors ramipril (0.01 and 1 mg/kg per day) and perindopril (0.01 mg/kg per day). Early-onset treatment with the high dose of ramipril inhibited aortic ACE activity, prevented the development of hypertension, increased aortic vasodilator responses to acetylcholine (10(-8) to 10(-6) mol/L), decreased vasoconstrictor responses to norepinephrine (10(-8) mol/L), and increased aortic cyclic GMP content by 160%. Low-dose ramipril inhibited aortic ACE activity and attenuated the aortic vasoconstrictor response to norepinephrine but had no effect on blood pressure. Low-dose treatment with ramipril and perindopril resulted in a significant increase in aortic cyclic GMP content by 98% and 77%, respectively. Long-term coadministration of the bradykinin B2-receptor antagonist Hoe 140 abolished the ACE inhibitor-induced increase in aortic cyclic GMP. Our data demonstrate that long-term treatment with ACE inhibitors can alter vascular function of compliance vessels independently of the antihypertensive action. The increase in aortic cyclic GMP was due to bradykinin potentiating the action of the ACE inhibitors.

Beneficial effects of bradykinin on myocardial energy metabolism and infarct size.

There is growing evidence for a local kallikrein-kinin system in the heart. In the ischemic heart the enhanced generation and release of kinins seem to have cardioprotective actions. In isolated rat hearts with ischemia-reperfusion injuries, perfusion with bradykinin reduces the duration and incidence of ventricular fibrillations, improves cardiodynamics, reduces release of cytosolic enzymes, and preserves energy-rich phosphates and glycogen stores. In anesthetized animals, intracoronary infusion of bradykinin is followed by comparable beneficial changes and limits infarct size. Inhibition of breakdown of bradykinin and related peptides induces similar beneficial cardiac effects. Treatment with angiotensin-converting enzyme (ACE) inhibitors such as ramipril increases cardiac kinins and reduces postischemic reperfusion injuries in isolated rat hearts as well as infarct size and remodeling in postinfarcted animals, respectively. Blockade of B2 kinin receptors increases ischemia-induced effects. In isolated hearts, ischemia-reperfusion injuries intensify with the B2 kinin receptor antagonist icatibant, which also abolishes the cardioprotective effects of ACE inhibitors and of exogenous bradykinin. Infarct size reduction by ACE inhibitors and bradykinin in anesthetized animals is reversed by icatibant. Kinins contribute to the cardioprotective effects associated with ischemic preconditioning. Preconditioning or bradykinin-induced antiarrhythmic and infarct size-limiting effects are attenuated by icatibant.

Ramipril prevents left ventricular hypertrophy with myocardial fibrosis without blood pressure reduction: a one year study in rats.

1. Angiotensin converting enzyme (ACE)-inhibitors have been demonstrated to be effective in the treatment of cardiac hypertrophy when used in antihypertensive doses. The aim of our one year study with an ACE-inhibitor in rats was to separate local cardiac effects produced by a non-antihypertensive dose from those on systemic blood pressure when an antihypertensive dose was used. 2. Rats made hypertensive by aortic banding were subjected to chronic oral treatment for one year with an antihypertensive dose of the ACE inhibitor, ramipril 1 mg kg-1 daily, (RA 1 mg) or received a low dose of 10 micrograms kg-1 daily (RA 10 micrograms) which did not affect high blood pressure. 3. Chronic treatment with the ACE-inhibitor prevented left ventricular hypertrophy in the antihypertensive rats as did the low dose which had no effects on blood pressure. Similar effects were observed on myocardial fibrosis. Plasma ACE activity was inhibited in the RA 1 mg but not in the RA 10 micrograms group although conversion of angiotensin (Ang) I to Ang II in isolated aortic strips was suppressed in both treated groups. Plasma catecholamines were increased in the untreated control group, but treatment with either dose of ramipril normalized the values. The myocardial phosphocreatine to ATP ratio (an indicator of the energy state in the heart) was reduced in the vehicle control group whereas the hearts from treated animals showed a normal ratio comparable to hearts from sham-operated animals. 4. After one year, five animals were separated from each group, treatment withdrawn, and housed for additional six months. In the RA 1 mg group, blood pressure did not reach the value of the control vehicle group and surprisingly, left ventricular hypertrophy and myocardial fibrosis did not recur in animals during withdrawal of treatment.5. These data show that long term ACE inhibitor treatment with ramipril in antihypertensive and non-antihypertensive doses prevented cardiac hypertrophy and myocardial fibrosis. This protective effect was still present after 6 months treatment withdrawal.

Ramiprilat increases bradykinin outflow from isolated hearts of rat.

To establish that bradykinin is formed in the heart we measured bradykinin in the venous effluent from rat isolated hearts perfused with Krebs-Henseleit buffer. In addition, we examined the effect on bradykinin outflow of the angiotensin converting enzyme (ACE) inhibitor, ramiprilat. From rat isolated normoxic hearts a bradykinin outflow of 0.85 +/- 0.1 ng ml-1 perfusate g-1 wet weight was measured. Perfusion with ramiprilat increased the bradykinin concentration to 2.8 +/- 0.3 ng ml-1 perfusate g-1 wet weight. During ischaemia bradykinin outflow maximally increased 8.2 fold to 7.0 +/- 0.5 ng ml-1 perfusate g-1, and in ramiprilat-perfused hearts 5.8 fold to 16.0 +/- 1.8 ng ml-1 perfusate g-1. In the reperfusion period bradykinin outflow normalized to values measured in the respective pre-ischaemic period. The presents data show that bradykinin is continuously formed in the rat isolated heart. Ischaemia increases bradykinin outflow from the heart. Presumably by inhibiting degradation of kinins, ACE inhibition significantly increased the bradykinin concentration during normoxia, ischaemia and reperfusion.

Release of nitric oxide from endothelial cells stimulated by YC-1, an activator of soluble guanylyl cyclase.

1 In this study we examined the endothelium-dependent effect of YC-1 - a benzyl indazole derivative which directly activates soluble guanylyl cyclase (sGC) - on vascular relaxation and nitric oxide (NO) and guanosine-3',5'-cyclic monophosphate (cyclic GMP) in endothelial cells. 2 In preconstricted rat aortic rings with intact endothelium, YC-1 produced a concentration-dependent relaxation. However, the concentration response curve was shifted rightward to higher concentrations of YC-1, when (i) the aortas were pre-treated with L-NG-nitroarginine methylester (L-NAME) or (ii) the endothelium was removed. 3 Incubation of bovine aortic endothelial cells (BAEC) with YC-1 produced a concentration-dependent NO synthesis and release as assessed using a porphyrinic microsensor. Pre-incubating cells with L-NAME or with 8-bromo-cyclic GMP decreased this effect indicating that the YC-1 stimulation of NO synthesis is due to an activation of nitric oxide synthase, but not to an elevation of cyclic GMP. No direct effect of YC-1 on recombinant endothelial constitutive NO synthase activity was observed. 4 The YC-1 stimulated NO release was reduced by 90%, when extracellular free calcium was diminished. 5 In human umbilical vein endothelial cells (HUVEC), YC-1 stimulated intracellular cyclic GMP production in a concentration- and time-dependent manner. Stimulation of cyclic GMP was greater with a maximum concentration of YC-1 compared to calcium ionophore A23187. Similar effects were observed in BAEC and rat microvascular coronary endothelial cells (RMCEC). 6 When HUVEC and RMCEC were pre-treated with L-NG-nitroarginine (L-NOARG), the maximum YC-1 stimulated cyclic GMP increase was reduced by >/=50%. 7 These results indicate, that beside being a direct activator of sGC, YC-1 stimulates a NO-synthesis and release in endothelial cells which is independent of elevation of cyclic GMP but strictly dependent on extracellular calcium. The underlying mechanism needs to be determined further.

Hoe 140 a new potent and long acting bradykinin-antagonist: in vitro studies.

1. Hoe 140 (D-Arg-[Hyp3, Thi5, D-Tic7, Oic8]bradykinin) is a new bradykinin (BK)-antagonist. It was tested in several in vitro assays and compared with D-Arg-[Hyp2,Thi5,8,D-Phe7]BK. 2. In receptor binding studies in guinea-pig ileum preparations, Hoe 140 showed an IC50 of 1.07 x 10(-9) mol l-1 and a KI value of 7.98 x 10(-10) mol l-1. 3. In isolated organ preparations Hoe 140 and D-Arg-[Hyp2,Thi5,8, D-Phe7]BK inhibited bradykinin-induced contractions concentration dependently, with IC50-values in the guinea-pig ileum preparation of 1.1 x 10(-8) mol l-1 and 3 x 10(-5) mol l-1, respectively. pA2 values in this tissue were 8.42 and 6.18, respectively. In the rat uterus preparation the IC50 value was 4.9 x 10(-9) mol l-1 for Hoe 140. D-Arg-[Hyp2, Thi5,8, D-Phe7]BK showed an IC50 of 4.0 x 10(-6) mol l-1. The IC50 values in the guinea-pig isolated pulmonary artery were 5.4 x 10(-9) mol l-1 and 6.4 x 10(-6) mol l-1, respectively. In the rabbit aorta no inhibitory effects on Des-Arg9-BK induced contractions were observed. 4. In cultured bovine endothelial cells, Hoe 140 antagonized (IC50 = 10(-8) mol l-1) bradykinin-induced endothelium-derived relaxing factor (EDRF) release and the bradykinin-induced increase in cytosolic free calcium (IC50 = 10(-9) mol l-1). 5. Hoe 140 (10 -7mol I1) totally suppressed the bradykinin-induced (10 8 to 10- mol I') prostacyclin (PGI2) release from cultured endothelial cells of bovine aorta. D-Arg-[Hyp2, Thi5'8, D-Phe7]BK (10- 7 mol I1- ) showed a weaker antagonism. 6. Taken together these results show that Hoe 140 is a highly potent bradykinin antagonist. It was two to three orders of magnitude more potent than D-Arg-[Hyp2, Thi5 8, D-Phe7]BK.

Neurochemical effects of the synthetic ACTH4-9-analog Hoe 427 (Ebiratide) in rat brain.

The ACTH4-9-analog Hoe 427 systemically injected in a dose range from 0.01-10 micrograms/kg caused a fall in acetylcholine (ACh) content in different brain areas of the rat. This effect occurred 0.5 hour after a single administration and lasted up to 24 hours. The decrease in ACh content induced by Hoe 427 was more pronounced when the animals were pretreated with dexamethasone (over 7 days 1 mg/kg SC, daily). Coadministration of the choline uptake inhibitor hemicholinium-3 (HC-3) and Hoe 427 potentiated the decrease in ACh content induced by HC-3. In the same dose range Hoe 427 acutely evoked an increase of the activity of the enzyme choline acetyltransferase as well as an elevation of brain cyclic GMP content. These data indicate that Hoe 427 enhances ACh metabolism in rat brain after systemic administration.

Learning and memory processes of an ACTH4-9 analog (ebiratide; Hoe 427) in mice and rats.

These experiments investigated the effects of the new ACTH4-9 analog ebiratide (Hoe 427) [H-Met(O2)-Glu-His-Phe-D-Lys-Phe-NH-(CH2)8-NH2 X 3 CH3COOH] on memory processes in mice and rats in five training tasks. With all five training and testing procedures (inhibitory avoidance test with ECS- or scopolamine-induced amnesia, up-hill avoidance, one-way shuttle box avoidance and eight-arm radial maze) ebiratide was most effective in a dose range of 1-10 micrograms/kg SC.

Enhancement of cytosolic calcium, prostacyclin and nitric oxide by bradykinin and the ACE inhibitor ramiprilat in porcine brain capillary endothelial cells.

We studied whether primary cultured porcine brain capillary endothelial cells (PBCEC) respond to bradykinin with an enhanced intracellular cytosolic calcium concentration [Ca2+]i with subsequent formation of nitric oxide (NO) and prostacyclin (PGI2). In addition we examined whether these cells synthetize and release kinins that may accumulate during angiotensin-converting enzyme (ACE) inhibition. [Ca2+]i was assessed by the fluorescent dye Fura-2, NO formation by determination of intracellular cyclic GMP and PGI2 by a specific radioimmunoassay for 6-ketoprostaglandin F1 alpha. Bradykinin and the ACE inhibitor ramiprilat concentration-dependently increased the formation of cyclic GMP which was completely prevented by the stereospecific inhibitor of NO synthase, NG-nitro-L-arginine. Also the specific B2-kinin receptor antagonist icatibant (Hoe 140) abolished the increase in cyclic GMP as well as the ramiprilat-induced increase in PGI2 formation. The data demonstrate the existence of B2-kinin receptors and ACE activity in PBCEC. Moreover PBCEC are capable of producing and releasing kinins in amounts that lead via stimulation of B2-kinin receptors to an enhanced [Ca2+]i as well as NO and PGI2 synthesis and release, provided that degradation of kinins is prevented by inhibition of endothelial ACE activity.

The bradykinin B2 receptor antagonist WIN 64338 inhibits the effect of des-Arg9-bradykinin in endothelial cells.

WIN 64338 (phosphonium, [[4-[[2-[[bis(cyclohexylamino) methylene] amino]-3-(2-naphthalenyl) 1-oxopropyl]amino]-phenyl]- tributyl, chloride, monohydrochloride) is the first potent nonpeptide competitive bradykinin B2 receptor antagonist as shown in classical pharmacological preparations with no activity in the rabbit aorta stimulated by the bradykinin B1 receptor agonist des-Arg9-bradykinin. In primary cultured bovine aortic endothelial cells, both bradykinin and des-Arg9-bradykinin stimulate the production of intracellular cyclic GMP, an index for the production of nitric oxide. Surprisingly, WIN 64338 did not inhibit bradykinin but abolished the effect of des-Arg9-bradykinin suggesting that kinin receptor antagonists do not necessarily discriminate between kinin receptor subtypes in an identical way in different tissues and species.

Effects of Hoe 065, a compound structurally related to inhibitors of angiotensin converting enzyme, on acetylcholine metabolism in rat brain.

Hoe 065, a compound structurally related to inhibitors of angiotensin converting enzyme, caused a fall in the content of acetylcholine (ACh) in different brain areas of the rat following i.p. administration in the range 0.03-30 mg/kg. This effect occurred 0.5 h after a single injection and lasted for at least 6 h. Simultaneous administration of the choline uptake inhibitor hemicholinium-3 (HC-3) with Hoe 065 potentiated the decrease in ACh content induced by HC-3. In the same dose range Hoe 065 acutely enhanced the activity of the enzyme choline acetyltransferase as well as the capacity of the high-affinity choline uptake system which is considered as the rate-limiting step in the synthesis of ACh. Cholinesterase activity in vivo was not altered by the compound. Hoe 065 produced a concurrent elevation of brain cyclic GMP content. Taken together, these results suggest that Hoe 065 acutely increases cholinergic activity within its physiological range, probably by means of an enhanced release of ACh.