Intact Vascular Endothelium Research Articles

Spatially structured cell populations process multiple sensory signals in parallel in intact vascular endothelium.

Blood flow, blood clotting, angiogenesis, vascular permeability, and vascular remodeling are each controlled by a large number of variable, noisy, and interacting chemical inputs to the vascular endothelium. The endothelium processes the entirety of the chemical composition to which the cardiovascular system is exposed, carrying out sophisticated computations that determine physiological output. Processing this enormous quantity of information is a major challenge facing the endothelium. We analyzed the responses of hundreds of endothelial cells to carbachol (CCh) and adenosine triphosphate (ATP) and found that the endothelium segregates the responses to these two distinct components of the chemical environment into separate streams of complementary information that are processed in parallel. Sensitivities to CCh and ATP mapped to different clusters of cells, and each agonist generated distinct signal patterns. The distinct signals were features of agonist activation rather than properties of the cells themselves. When there was more than one stimulus present, the cells communicated and combined inputs to generate new distinct signals that were nonlinear combinations of the inputs. Our results demonstrate that the endothelium is a structured, collaborative sensory network that simplifies the complex environment using separate cell clusters that are sensitive to distinct aspects of the overall biochemical environment and interactively compute signals from diverse but interrelated chemical inputs. These features enable the endothelium to selectively process separate signals and perform multiple computations in an environment that is noisy and variable.

English

There are reports of the presence of vasodilatory alkaloids in Heimia salicifolia extracts. The action mechanisms of the potential antihypertensive effect of such alkaloids have not however, been elucidated. The objective of the present study was to corroborate the antihypertensive and vasorelaxant activities of the isolated alkaloids from H. salicifolia, and to characterize their vasorelaxant actions. A chloroform extract (HSCE) was obtained from H. salicifolia. The alkaloids were separated by thin layer chromatography, extracted from silica gel, and evaluated using spectroscopy. The alkaloid with the most potent vasorelaxant activity was identified as lythrine. The antihypertensive effect of the HSCE was corroborated on normotensive rats and on animals with Nω-nitro-L-arginine-methyl ester (L-NAME) induced hypertension. The action mechanisms of the HSCE and lythrine were studied on isolated and perfused rat mesenteric vascular bed (MVB) preparations. HSCE administration produced a concentration-dependent relaxation, but in preparations without vascular endothelium, the relaxant response to HSCE was significantly diminished. In MVB preparations with intact vascular endothelium, pre-contracted with phenylephrine or L-NAME, perfusion with lythrine produced concentration-dependent relaxation; a similar effect was produced by acetylcholine. Wortmannin (phosphatidylinositol 3-kinase inhibitor) and methylene blue (guanylate cyclase inhibitor) decreased the relaxant effect of lythrine. These data suggest that the vascular relaxation induced by alkaloids isolated from H. salicifolia is dependent on the activation of the nitric oxide/guanylate cyclase pathway. Key words: Heimia salicifolia, lythrine alkaloid, hypertension, Nω-nitro-L-arginine-methyl ester (L-NAME), mesenteric vascular bed. &nbsp

Effects of low-frequency ultrasound and microbubbles on angiogenesis-associated proteins in subcutaneous tumors of nude mice

It has been shown that 1 and 3 MHz low-intensity ultrasound was able to affect the fragile and leaky angiogenic blood vessels in a tumor. However, the biological effects of 21kHz low-intensity ultrasound on tumors remain unclear. The aim of the present study was to explore the effects of 21kHz ultrasound with microbubbles on the regulation of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2) and apoptosis in subcutaneous prostate tumors in nude mice. The study included three parts, each with 20 tumor-bearing nude mice. Twenty nude mice were divided into four groups: control (sham treatment), microbubble ultrasound contrast agent (UCA), low-frequency ultrasound (US) and US+UCA groups. The UCA used was a microbubble contrast agent (SonoVue). The parameter of ultrasound: 21kHz, an intensity of 26mW/cm2, 40% duty cycle (on 2sec, off 3sec), 3min, once every other day for 2 weeks. In the first study, all subcutaneous tumors were examined by contrast-enhanced ultrasonography (CEUS) at the initiation and completion of the experiments. Peak intensity (PI), time to peak intensity (TTP) and area under the curve (AUC) on the time intensity curve (TIC) were analyzed. In the second study, the intensity of VEGF and COX-2 protein expression in the vascular endothelium and cytoplasm was evaluated using immunohistochemistry and laser confocal microscopy. In the third study, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used for the evaluation of cell apoptosis in tumor tissues. The tumor cells and vasculature were examined by transmission electron microscopy (TEM). Only in the US+UCA group, PI and AUC decreased. The intensity of COX-2 and VEGF in the US+UCA group in immunohistochemical staining and laser confocal microscopy was lower compared to that of the other three groups. More cell apoptosis was found in the US+UCA group compared to the other 3 groups. In the control, UCA and US groups, the tumors had intact vascular endothelium and vessel lumens in TEM. However, lumen occlusion of vessels was observed in the US+UCA group. Twenty-one kHz low-intensity ultrasound with microbubbles may have anti-angiogenic effects on subcutaneous tumors in nude mice.

Assessing vascular endothelial function using frequency and rank order statistics

Using frequency and rank order statistics (FROS), this study analyzed the fluctuations in arterial waveform amplitudes recorded from an air pressure sensing system before and after reactive hyperemia (RH) induction by temporary blood flow occlusion to evaluate the vascular endothelial function of aged and diabetic subjects. The modified probability-weighted distance (PWD) calculated from the FROS was compared with the dilatation index (DI) to evaluate its validity and sensitivity in the assessment of vascular endothelial function. The results showed that the PWD can provide a quantitative determination of the structural changes in the arterial pressure signals associated with regulation of vascular tone and blood pressure by intact vascular endothelium after the application of occlusion stress. Our study suggests that the use of FROS is a reliable noninvasive approach to the assessment of vascular endothelial degeneration in aging and diabetes.

Red Blood Cells As a Novel Mediator of Chronic Inflammation in Diet-Induced Obesity: Implications for Atherosclerosis

AbstractAbstract 3198 Background:Red blood cell (RBC) extravasation contributes to the growth of atherosclerotic plaque, and is associated with plaque rupture. High Fat Diet (HFD) fuels systemic inflammation by promoting monocyte activation and their recruitment/transendothelial migration. RBC bind chemokines such as monocyte chemotactic protein-1 (MCP-1) via Duffy Antigen Receptor for Chemokines (DARC). While it was previously reported that HFD may impact RBC cholesterol content, very little is known about the impact – if any – of HFD on RBC function(s). Hence, we studied whether HFD affects biochemical and functional properties of RBC in ways potentially relevant to the progression of atherosclerosis. Methods and Results:Wild type (WT) C56BL6/J mice were fed either chow (10% total fat) or HFD (60% total fat) for 312 weeks. MCP-1 levels were measured in plasma before and after the release of DARC-bound MCP-1 by heparin. Released MCP-1 was 1.5 fold higher in HFD RBC (12 weeks on diet, n=3) compared to chow RBC. Levels of intracellular reactive oxygen species (ROS) were measured by DCFH fluorescence using flow cytometry, and were increased in HFD RBC (17 weeks on diet, n=3) by ∼1.2 fold compared to chow RBC (p<0.05). We also observed a 1.5 fold increase in external phosphatidylserine (PS) in HFD RBC (12 weeks on diet, n=3) as revealed by Annexin V binding (flow cytometry). In vitro erythrophagocytosis was assayed by incubating thioglycollate-induced peritoneal macrophages from WT mice with calcein-AM labeled RBC obtained from mice on HFD (12 weeks on diet, n=3) or chow. A ∼1.5 fold (p<0.05) increase in phagocytosis was observed for HFD RBC compared to chow RBC. When HFD RBC served as a source of chemoattractant(s), we observed a ∼1.4 fold (p<0.05) increase (compared to chow RBC) in the number of monocytes undergoing transendothelial migration in a Boyden chamber assay. Experiments performed on RBC from LDLr −/− mice fed either HFD or chow for 12 weeks (n=3), displayed the fold changes analogous to those observed in RBC from WT mice with respect to ROS levels, transendothelial monocyte migration, and PS externalization but a significant increase in RBC phagocytosis of ∼1.7 fold (p<0.05). The increased PS exposure was associated with an increase in splenic uptake of RBC: calcein-AM labeled packed RBC (chow or HFD) were injected retroorbitally into WT mice maintained on chow and after 24 hrs, peripheral blood was removed by cardiac perfusion, spleens harvested, embedded in OCT media, and 10 mm sections were analyzed using Image J software. Macrophages located predominantly in splenic sinuses engulfed ∼3 fold more HFD RBC (12 weeks on diet, n=3) compared to chow RBC (p<0.05). Microarray analysis was then performed on peritoneal macrophages derived from HFD mice that were incubated with either HFD RBC or chow RBC for 4 hrs (results validated by qRT-PCR). Interestingly, several chemokines such as Il-1b, Ccl3, and Cxcl2 were upregulated in HFD macrophages that engulfed HFD RBC compared to those that engulfed chow RBC (3 fold, 3 fold, and 12 fold, respectively). RBC deformability, a crucial characteristic enabling RBC to traverse through narrow capillaries/splenic sinuses, was measured using ektacytometry. Deformability expressed as elongation index was decreased in HFD RBC compared to chow RBC, especially at intermediate shear stress (2 – 20 Pa). Finally, when freshly harvested aortic segments were incubated with packed RBC (HFD or chow), washed, and exposed to pre-labeled fluorescent WT murine macrophages, there was an enhancement of macrophage adhesion to the luminal endothelium when HFD RBC were used (∼3 fold, p<0.05). Conclusions:We here show that HFD elicits an increase in surface levels of MCP-1 in RBC, which is associated with an enhanced macrophage adhesion to the intact vascular endothelium and increased transendothelial migration in vitro. Further, HFD increases ROS levels and PS externalization in RBC, and HFD RBC exhibit an enhanced splenic uptake in vivo. These effects of HFD on circulating RBC are likely to promote chronic inflammation, rendering RBC a heretofore unknown contributor to local as well as systemic changes that lead to atherosclerosis. Disclosures:No relevant conflicts of interest to declare.

TRPV4 sparklets‐Elementary Ca2+ signals underlying endothelial‐dependent vascular function

Endothelial cells (ECs) play an important role in regulation of vascular tone. Elevated intracellular Ca2+ is central to EC function. We report the discovery of local Ca2+ signals (“sparklets”) in the intact vascular endothelium of resistance arteries that represent Ca2+ influx through single TRPV4 (Transient receptor potential vanilloid 4) channels. We used spinning disk confocal imaging for recording the Ca2+ sparklets in third‐order mouse mesenteric arteries (MAs). Activation of TRPV4 sparklets with GSK1016790A (GSK, TRPV4 agonist, 10 nM) was cooperative, with fewer than two sparklet sites (&lt;8 channels) per cell. Diameter studies in pressurized mouse MAs showed that GSK caused maximal, nitric oxide (NO)‐independent dilation through activation of EC intermediate (IK)‐ and small (SK)‐conductance, Ca2+‐sensitive K+ channels (n=5–7). GSK also increased IK‐ and SK‐channel current densities in isolated ECs (n=5). These results support a novel concept that Ca2+ influx through a single TRPV4 channel is leveraged by the combined amplifier‐effect of cooperative channel activation and high Ca2+ sensitivity of IK/SK channels to cause vasodilation, and thus provide a new paradigm for transcellular signaling.

Elementary TRPV4 Ca 2+ events in intact vascular endothelium

Transient receptor potential vanilloid 4 (TRPV4) channel serves as a Ca2+ influx pathway in endothelial cells (ECs). The objective of this study was to identify elementary TRPV4 Ca2+ events in vascular ECs. We used third-order mesenteric arteries (MAs) from mice that express Ca2+ biosensor (GCaMP2) selectively in ECs. TRPV4 agonist GSK1016790A (GSK, 10 nM) produced EC-dependent dilation of pressurized MAs. High speed confocal imaging of slit-open MAs revealed that TRPV4 agonists (GSK, 4α-PDD, 11,12-EET) activate local Ca2+ events (“TRPV4 Ca2+ sparklets”) in ECs in absence of Ca2+ release from intracellular stores. Fractional fluorescence changes (ΔF/F0) for 19 event sites showed a quantal level of 0.22 ± 0.03. Mean open probability (NPs, N = number of quanta, Ps = probability of occurrence) of the sparklets at a site was 0.46 ± 0.06 (n = 10 sites), 0.19 ± 0.03 (n = 5 sites) and 0.57 ± 0.19 (n = 5 sites) for GSK (10 nM), 4α-PDD (5 μM) and 11, 12-EET (1 μM), respectively. TRPV4 inhibitor HC067047 (1 μM) significantly reduced NPs of GSK-induced sparklets to 0.16 ± 0.05 (n = 5 sites, p<0.05). In conclusion, this is the first detection of elementary TRPV4 Ca2+ sparklets that initiate EC-dependent vasodilation of resistance arteries. Supported by AHA-PHA 10POST3690006 (SKS) and NIH HL44455 (MTN).

Evaluation Of A Haemostatic Agent In Rabbits

Topical hemostatic agents are applied locally to areas of injured vascular endothelium to control local bleeding. Ankaferd Blood Stopper (ABS) has gained approval in Turkey and Bosnia-Herzegovina as a topical haemostatic agent for external post-surgical and post-dental surgery bleeding. The safety of topical use of ABS has been demonstrated in numerous in vitro and in vivo animal models, as well as in a clinical Phase I trial in humans. ABS, besides its haemostatic activity, also has in vitro anti-infectious and anti-neoplastic effects. To assess potential detrimental effects of intravenous administration of ABS into intact systemic circulation in a rabbit experimental model, one milliliter of ABS was administered intravenously into the systemic circulation of twelve rabbits which were included in the study via the marginal ear vein. Animals were observed for 1 hr before euthanasia was performed by administering 40 mg of intracardiac suxamethonium chloride. In the event of death (cardiopulmonary arrest) before the end of the planned observation period of 60 minutes, time of death was recorded and histopathological examination of the liver and spleen was commenced. Ten rabbits were alive by the end of the planned observation period, without showing any clear signs of discomfort, whereas two animals died within five minutes after systemic administration of intravenous ABS. Postmortem histopathological examination of the livers and spleens of all animals' revealed findings consistent with hepatic venous outflow obstruction. Systemic intravascular administration of ABS into intact vascular endothelium should never be performed in any setting. Further experimental and clinical studies on this liquid hemostatic agent should proceed by accepting ABS as purely a topical haemostatic agent, to be applied solely to areas of injured vascular endothelium.

Relaxant effects of the aqueous leaf extract of &lt;i&gt;cassia occidentailis&lt;/i&gt; on rat aortic rings

The relaxant effects of an aqueous extract of the leaf of plant cassia occidentalis (C.O.) were investigated in rat aortic rings with or without intact endothelium. The extract inhibited contraction elicited by noradrenaline (NA) and Potassium Chloride (KCI) dose dependently. It also relaxed aortic rings precontracted with 10-7 M NA and 50m M KCI. This relaxation did not require the presence of an intact vascular endothelium and was not affected by indomethacin (Prostacylin inhibitor) and methylene blue.

Platelet aggregation responses are critically regulated in vivo by endogenous nitric oxide but not by endothelial nitric oxide synthase

Although exogenous nitric oxide (NO) clearly modifies platelet function, the role and the source of endogenous NO in vivo remain undefined. In addition, endothelial NO synthase (NOS-3) critically regulates vessel tone but its role in modulating platelet function is unclear. In this paper we have investigated the roles of endogenous NO and NOS-3 in regulating platelet function in vivo and determined the functional contribution made by platelet-derived NO. We used a mouse model for directly assessing platelet functional responses in situ in the presence of an intact vascular endothelium with supporting in vitro and molecular studies. Acute NOS inhibition by N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME) enhanced platelet aggregatory responses to thrombin and platelets were shown to be regulated primarily by NO sources external to the platelet. Elevation of endogenous NOS inhibitors to mimic effects reported in patients with cardiovascular diseases did not enhance platelet responses. Platelet responsiveness following agonist stimulation was not modified in male or female NOS-3(-/-) mice but responses in NOS-3(-/-) mice were enhanced by L-NAME. Platelets are regulated by endogenous NO in vivo, primarily by NO originating from the environment external to the platelet with a negligible or undetectable role of platelet-derived NO. Raised levels of endogenous NOS inhibitors, as reported in a range of diseases were not, in isolation, sufficient to enhance platelet activity and NOS-3 is not essential for normal platelet function in vivo due to the presence of bioactive NO following deletion of NOS-3.

Mechanisms responsible for pulmonary hypertension

Mechanisms responsible for pulmonary hypertension

123 APPLICATION OF BIOLOGICAL FEEDBACK SYSTEMS AND OTHER METHODS OF EXAMINATIONS FOR CONTROL OF EFFECTS OF LIGHT THERAPY

of vascular walls are subjects of light exposure during the intravenous laser blood irradiation treatment. In the current study the influence of the laser light on endothelial cells and platelets was investigate. HUVEC endothelial cell culture was irradiated by HeNe laser. The expression of E-selectin was detected as a sign of activation of adhesive function of the cells after 20min of laser irradiation. Higher adhesion rate of intact platelets to irradiated endothelial cells was revealed. So, activation of endothelial cells and higher ability of adhesion of platelets were results of laser irradiation of endothelial cells. Platelet response to laser irradiation was completely different. Inhibition of platelet activation by TRAP due to decrease of expression of P-selectin and weaker ability of binding fibrinogen by GPIIbIII membrane receptor were detected. Inhibition of aggregation induced by different inductors (ADP, ristocetin, adrenalin, collagen) and inhibition of adhesion on extracellular matrix, collagen covered surfaces as well as intact vascular endothelium was detected. The inhibitory effect of laser irradiation on platelets was mediated by photoactivation of guanilatcyclase, higher amount of cGMP and inhibition of intracellular reactions with proteincinase C participation. As a conclusion, the different way of reacting of endothelial cells and platelets on laser irradiation is an important factor, supporting circulatory hemostasis during intravenous laser blood irradiation.

Letter to the editor: Infarct size measurements are critically important when comparing interventions affecting ventricular remodeling

REPLY: Dr. Lygate (5) has suggested that the variability observed in infarct size in the surgical mouse myocardial infarction model (10 –70%) (1, 7) mandates larger sample sizes than used in our study (9). Although we agree that variable infarct size certainly occurs with this model, our presented data show clear, statistically significant differences with the given sample sizes. Our protocol may reduce variability in infarct size by careful attention to a proximal ligation of the left coronary immediately at the site where it emerges from under the left atrium as well as by eliminating mice that do not have a clear area of distal blanching of myocardium after immediate ligation (4, 8, 9). The more distal the ligation is made, the more the variability in coronary anatomy of the mouse heart impacts infarct size. Thus the referenced study by Patten et al. (7), which stated that the suture on the left coronary was placed approximately midway between the apex and base of the left ventricle, likely introduced greater variability in infarct size than we observed. Another study referenced by Dr. Lygate further makes this point in that Takagawa et al. (10) systematically created large infarctions by using proximal left coronary ligations (4 mm from apex) and small infarctions by distal ligations (2 mm from apex). We conclude that with careful attention to surgical technique, the range of infarct sizes can be much smaller than the 10 –70% suggested by Dr. Lygate and that with the techniques used in our study, statistically significant results with the stated sample sizes were obtained. Second, Dr. Lygate questions the validity of the infarct size measurements made at the mid-papillary muscle level. This approach is a common technique used in the literature, including a contemporary study (2). Although we certainly concede that absolute quantification of size of the infarction relative to the total left ventricle would require additional sampling, our purpose was to compare two groups of animals assessed in the same fashion at the mid-papillary level. This was the region where the samples were taken for assessment of apoptosis, so it was desirable to have the closest matched regions for apoptosis and infarct size measurements. Using this uniform sampling method, we observed statistically significant differences. Finally, Dr. Lygate raises the question as to whether the decrease in apoptosis, hypertrophy, and fibrosis were direct effects of ESC treatment or simply reflected the reduction in infarct size. Dr. Lygate states that the extent of apoptosis correlates directly with infarct size and cites relevant literature (3, 7); however, these references simply look at apoptosis levels following infarction without intervention. A broader examination of the literature in which intervention groups are compared with control myocardial infarction groups reveals that a correlation between infarct size and the extent of apoptosis is oftentimes not present (2, 6). To begin to address this issue directly for apoptosis in our study, we provided data in Figure 1H (9) showing that there is not a simple correlation between infarct size and apoptotic nuclei and that the two groups of data are clearly separate. Nevertheless, we acknowledge that fully understanding the mechanisms underlying the observed effects will require substantial future studies.

Reply to “Letter to the editor: ‘Are voltage-dependent ion channels involved in the endothelial cell control of vasomotor tone?’”

reply: The letter from Welsh and colleagues ([6][1]) raises many points, but we will respond here only to the major issues. We find it scientifically unacceptable to simply deny our citations reporting identification of ion channels in cultured cells. Do the correspondents wish to deny the existence

Diabetes mellitus as a prothrombotic condition

Diabetes mellitus (DM) is characterized by fasting hyperglycaemia and a high risk of atherothrombotic disorders affecting the coronary, cerebral and peripheral arterial trees. The risk of myocardial infarction (MI) is 3-5 fold higher in Type 2 DM and a DM subject with no history of MI has the same risk as a non-DM subject with a past history of MI. In total around 70% of deaths are vascular with poorer outcomes to both acute events and cardiological interventions. It was proposed that clustering of vascular risk factors (hyperinsulinaemia, dysglycaemia, dyslipidaemia and hypertension) around insulin resistance (IR) accounted for the increase in risk with Type 2 DM. The importance of this became apparent with the recognition that risk clustering occurs in normoglycaemic and impaired glucose tolerance (IGT) subjects with IR, in total around 25% of the population in addition to long-standing Type 1 subjects with renal disease. Evidence indicates that thrombotic risk clustering also occurs in association with IR, suppression of fibrinolysis due to elevated concentrations of the fibrinolytic inhibitor, plasminogen activator inhibitor-1 (PAI-1) is invariable with IR and there is evidence that this is regulated by the effects of triglyceride on the PAI-1 gene promoter. Other studies indicated that prothrombotic risk (coagulation factors VII, XII and fibrinogen) also associates with the IR syndrome. The development of endothelial cell dysfunction with suppression of nitric oxide and prostacyclin synthesis, combined with platelet resistance to the anti-aggregatory effects of these hormones leads to loss of control over platelet activation. In addition, hyperglycaemia and glycation have marked effects on fibrin structure function, generating a clot which has a denser structure, resistant to fibrinolysis. The combination of increased circulating coagulation zymogens, inhibition of fibrinolysis, changes in fibrin structure/function and alterations in platelet reactivity creates a thrombotic risk clustering which underpins the development of cardiovascular disease.

Regulation of pressure-activated channel in intact vascular endothelium of stroke-prone spontaneously hypertensive rats

The pressure-activated cation channel (PAC), a novel type of mechanosensitive channel, has been suggested to act as a mechanosensor in aortic endothelium. In experimental hypertension, PAC function was up-regulated in the established phase of high blood pressure. This association of altered PAC function and elevated arterial pressure suggests that PAC function is regulated by alterations in blood pressure. In the present study, we electrophysiologically investigated PAC function in intact endothelium of aorta (EA) and mesenteric artery (EMA) from stroke-prone spontaneously hypertensive rats (SHRSP), SHRSP after 4 weeks of treatment with quinaprilat (10 mg/kg/day), and normotensive Wistar-Kyoto (WKY) rats. In untreated SHRSP and WKY rats, systolic blood pressure (SBP) was 201 ± 3 mm Hg and 142 ± 3 mm Hg, respectively. In quinaprilat-treated SHRSP, SBP was lowered to 135 ± 5 mm Hg. Apparent PAC density (percentage of patches with PAC activity) in EA of untreated SHRSP (63.7% ± 7.3%) was 2.4-fold higher than in WKY rats (26.0% ± 5.0%). In contrast, no significant PAC up-regulation was detected in EMA of SHRSP (15.7% ± 4.2%) compared with WKY rats (12.0% ± 3.9%). In EA of quinaprilat-treated normotensive SHRSP, PAC density (27.1% ± 5.2%) was lowered to levels found in normotensive WKY rats. Unitary conductance and pressure sensitivity of PAC were not altered in either hypertensive or normotensive rats. Taken together, hypertension-induced increases of endothelial PAC density can be completely reversed by antihypertensive therapy. The PAC up-regulation in EA was interpreted as a compensatory mechanism to enhance Ca 2+-influx and subsequently the synthesis of vasodilatory factors. This mechanism is missing in EMA of SHRSP, which might contribute to high blood pressure in this rat model of severe genetic hypertension.

Endothelium-dependent potentiation of prostaglandin F2alpha-induced contractions by (+/-)-[6]-gingerol is inhibited by cyclooxygenase- but not lipoxygenase-inhibitors in mouse mesenteric veins.

The mechanism of potentiation of prostaglandin (PG) F2alpha-induced contraction of mouse mesenteric veins by (+/-)-[6-gingerol was investigated in vitro. (+/-)-[6]-Gingerol (0.3mM) potentiated the maximal contraction response elicited by PGF2alpha (0.28 mm) in the presence of intact vascular endothelium, but not in its absence (de-endothelialized preparations). The potentiating effect was completely inhibited by cyclooxygenase inhibitors (0.2 mm aspirin and 0.2 mm indomethacin) and partly by calcium antagonists (2 microM verapamil, 8 nM nitrendipine and 1 microM ryanodine), but not inhibited by nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor and ONO-3708, a thromboxane (TX) A2 antagonist. The potentiation by (+/-)-[6]-gingerol is also observed in mesenteric veins of streptozotocin-diabetic mice where the enhancement of PGF2alpha-induced contraction is caused mainly by activation of lipoxygenase. The potentiation of PGF2alpha-induced contraction by (+/-)-[6]-gingerol may be caused by a cyclooxygenase-dependent release of vasoconstrictors, other than PGF2alpha and TXA2, or by inhibiting vasorelaxants released from endothelial cells of mouse mesenteric veins.

2426 Simultaneous optical recording of electrical activity with simple cell resolution from the mammalian enteric nervous system

Currently, it is not possible to prevent essential hypertension and this presents a challenge to the clinician, pharmacologist, and medicinal chemist to discover adequate therapies. This chapter discusses the beneficial effects of drug therapy in the management of hypertension, the significance of catecholamine levels in hypertension, role of the sympathoadrenal axis in hypertension, and the need for intact vascular endothelium for vascular responses to a number of agents. A cautionary note offered that the levels in mixed venous blood are unreliable indicators of sympathetic neural activity in hypertension. Current evidence supports the hypothesis that converting enzyme (CEI) exerts their hypotensive effects primarily by inhibition of circulating and tissue-bound converting enzyme. A summary of the pharmacology of enalapril (MK-421) has appeared along with an account of the clinical studies done with lisinopril (MK-521) that suggest this drug will be suitable for once-a-day anti-hypertensive therapy. Analogs of enalapril that have appeared include the perhydroindole derivative. New evidence suggests certain calcium entry blockers (CEB) affect neural regulation of blood vessels at several sites. Studies in anesthetized dogs indicate that nifedipine increases and verapamil decreases the sensitivity of carotidsinus baroreceptors apparently by interference with a calcium-dependent and a sodium-dependent mechanism, respectively. New studies have examined the interaction of various CEB with α-adrenoceptors and their effect on the processes mediated by a-adrenoceptors. The (+) and (-) antipodes of verapamil, nicardipine, and (+) D-600 showed similar inhibition of radioligand binding to al-adrenoceptors, whereas diltiazem and nifedipine showed a very low level of activity.

2425 Median preoptic neurons projecting to the CVLM catecholaminergic area receive synaptic inputs of the nerve terminals

Currently, it is not possible to prevent essential hypertension and this presents a challenge to the clinician, pharmacologist, and medicinal chemist to discover adequate therapies. This chapter discusses the beneficial effects of drug therapy in the management of hypertension, the significance of catecholamine levels in hypertension, role of the sympathoadrenal axis in hypertension, and the need for intact vascular endothelium for vascular responses to a number of agents. A cautionary note offered that the levels in mixed venous blood are unreliable indicators of sympathetic neural activity in hypertension. Current evidence supports the hypothesis that converting enzyme (CEI) exerts their hypotensive effects primarily by inhibition of circulating and tissue-bound converting enzyme. A summary of the pharmacology of enalapril (MK-421) has appeared along with an account of the clinical studies done with lisinopril (MK-521) that suggest this drug will be suitable for once-a-day anti-hypertensive therapy. Analogs of enalapril that have appeared include the perhydroindole derivative. New evidence suggests certain calcium entry blockers (CEB) affect neural regulation of blood vessels at several sites. Studies in anesthetized dogs indicate that nifedipine increases and verapamil decreases the sensitivity of carotidsinus baroreceptors apparently by interference with a calcium-dependent and a sodium-dependent mechanism, respectively. New studies have examined the interaction of various CEB with α-adrenoceptors and their effect on the processes mediated by a-adrenoceptors. The (+) and (-) antipodes of verapamil, nicardipine, and (+) D-600 showed similar inhibition of radioligand binding to al-adrenoceptors, whereas diltiazem and nifedipine showed a very low level of activity.

2424 Changes in the smooth muscle of the guinea-pig vas deferens by thermal stress

Currently, it is not possible to prevent essential hypertension and this presents a challenge to the clinician, pharmacologist, and medicinal chemist to discover adequate therapies. This chapter discusses the beneficial effects of drug therapy in the management of hypertension, the significance of catecholamine levels in hypertension, role of the sympathoadrenal axis in hypertension, and the need for intact vascular endothelium for vascular responses to a number of agents. A cautionary note offered that the levels in mixed venous blood are unreliable indicators of sympathetic neural activity in hypertension. Current evidence supports the hypothesis that converting enzyme (CEI) exerts their hypotensive effects primarily by inhibition of circulating and tissue-bound converting enzyme. A summary of the pharmacology of enalapril (MK-421) has appeared along with an account of the clinical studies done with lisinopril (MK-521) that suggest this drug will be suitable for once-a-day anti-hypertensive therapy. Analogs of enalapril that have appeared include the perhydroindole derivative. New evidence suggests certain calcium entry blockers (CEB) affect neural regulation of blood vessels at several sites. Studies in anesthetized dogs indicate that nifedipine increases and verapamil decreases the sensitivity of carotidsinus baroreceptors apparently by interference with a calcium-dependent and a sodium-dependent mechanism, respectively. New studies have examined the interaction of various CEB with α-adrenoceptors and their effect on the processes mediated by a-adrenoceptors. The (+) and (-) antipodes of verapamil, nicardipine, and (+) D-600 showed similar inhibition of radioligand binding to al-adrenoceptors, whereas diltiazem and nifedipine showed a very low level of activity.