bluuebunny/crossref_metadata_2025 huggingface dataset:
Endothelial cell dysfunction occurs very early following trauma-hemorrhage and persists despite fluid resuscitation
Authors: Wang P. , Ba Z. F. , Chaudry I. H.
Published: December 2017

Although hemorrhage produces alterations in hemodynamics and cellular functions, it remains unknown if endothelial cell function is depressed in a nonheparinized model of trauma-hemorrhage and resuscitation. To study this, rats underwent a 5-cm midline laparotomy (i.e., trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximal bleed-out volume was returned in the form of Ringer lactate (RL). They were then resuscitated with four times the volume of the shed blood with RL over 60 min. At the time of maximal bleed out (approximately 50 min from the onset of hemorrhage), 1.5, and 4 h after the completion of resuscitation, aortic rings (approximately 2.5 mm in length) were isolated and mounted in organ chambers. Dose responses for an endothelium-dependent vasodilator (acetylcholine) and endothelium-independent vasodilator (nitroglycerin) were determined. The results indicate that endothelium-dependent relaxation was depressed at the time of maximal bleed out and persisted even after resuscitation. However, there was no significant difference in nitroglycerin-induced relaxation at any point during the study period. In addition, hypoxia-induced contraction, a process mediated by endothelium-derived contracting factor, decreased significantly following hemorrhage and resuscitation. Thus endothelial cell dysfunction (i.e., reduced release of endothelium-derived relaxing and contracting factors) occurs very early after trauma-hemorrhage and persists despite fluid resuscitation.
Mitogenic effects of ATP on vascular smooth muscle cells vs. other growth factors and sympathetic cotransmitters
Authors: Erlinge D. , Yoo H. , Edvinsson L. , Reis D. J. , Wahlestedt C.
Published: December 2017

The sympathetic nervous system has been shown to exert a trophic influence on vascular smooth muscle cells (VSMC). Therefore, we studied the growth-regulating effects of the sympathetic cotransmitters ATP, neuropeptide Y (NPY), and norepinephrine (NE). ATP in concentrations of 1-100 microM greatly increased the incorporation of [3H]thymidine in VSMC from rat aorta and vena cava. ATP also increased cell number and total protein content. The maximal effect on [3H]thymidine incorporation was greater than for epidermal growth factor (20 ng/ml) or insulin (1 microgram/ml) and approximately one-half that of 10% fetal calf serum. The potency series of other nucleotides and analogues of ATP was ATP > beta, gamma-methyleneATP (AMP-PCP) > ADP > adenosine > alpha, beta- methyleneATP (AMP-CPP) > 2-methylthioATP, indicating involvement of a P2 receptor, however, it does not meet proposed pharmacological criteria of either the P2x or P2y subclass. Several proposed P2 receptor antagonists were without effect. The effect of ATP could be mediated by a "nucleotide receptor," since UTP also stimulated [3H]thymidine incorporation. In our model, there was a strong correlation between the mitogenic effects of ATP, AMP-CPP, AMP-PCP, and UTP and their ability to stimulate influx of extracellular Ca2+ (Ca2+o). Moreover, the mitogenic effect of ATP was increased by high concentrations of Ca2+o. Taken together with data showing the lack of involvement of several other second-messenger systems, this indicates a critical role for Ca2+o in mediating the mitogenic effects of ATP. Amiloride, known to inhibit the action of several growth factors, also inhibited ATP-induced mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Regulation of Na-K-ATPase gene expression by aldosterone in vascular smooth muscle cells
Authors: Oguchi A. , Ikeda U. , Kanbe T. , Tsuruya Y. , Yamamoto K. , Kawakami K. , Medford R. M. , Shimada K.
Published: December 2017

Na-K-adenosinetriphosphatase (ATPase) activity profoundly influences vascular cell excitability, contractility, and volume regulation. The recent finding of mineralocorticoid hormone receptors in vascular tissue suggests the possibility that Na-K-ATPase gene expression in vascular tissue is regulated by the mineralocorticoid aldosterone. In this study, we investigated Na-K-ATPase gene expression by aldosterone in cultured rat vascular smooth muscle cells (VSMC). Na-K-ATPase alpha 1- and beta 1-isoform mRNAs, but not alpha 2- and alpha 3-isoform mRNAs, were expressed in cultured rat VSMC. Aldosterone caused a 2.3-fold increase in the alpha 1 mRNA and a 4.7-fold increase in the beta 1 mRNA accumulation with peak elevations at 24 and 6 h, respectively. Aldosterone induced the alpha 1 mRNA expression at physiological concentrations (half-maximum effective concentration = 2-3 nM), consistent with the binding of aldosterone to mineralocorticoid hormone receptors. The augmented alpha 1 mRNA expression by aldosterone was associated with a twofold increase in the alpha 1-subunit protein accumulation. Pretreatment of VSMC with cycloheximide caused a 10-fold increase in the alpha 1 mRNA expression, and the aldosterone-mediated alpha 1 mRNA accumulation was not observed in the presence of cycloheximide. Transfection experiments with the luciferase reporter gene revealed that aldosterone response sequences are located within the 5'-flanking regions of the alpha 1-isoform gene. These data demonstrate that the mineralocorticoid aldosterone directly stimulates Na-K-ATPase gene expression and protein accumulation in VSMC.
Sodium current in isolated human ventricular myocytes
Authors: Sakakibara Y. , Furukawa T. , Singer D. H. , Jia H. , Backer C. L. , Arentzen C. E. , Wasserstrom J. A.
Published: December 2017

Although fast sodium current (INa) plays a major role in the generation and conduction of the cardiac impulse, the electrophysiological characteristics of INa in isolated human ventricular myocytes have not yet been fully described. We characterized the human ventricular INa of enzymatically isolated myocytes using whole cell voltage-clamp techniques. Sixty myocytes were isolated from ventricular specimens obtained from 22 patients undergoing open-heart surgery. A low temperature (17 degrees C) and Na+ concentration in the external solution (5 or 10 mM) allowed good voltage control and facilitated the measurement of INa. Cs+ was substituted for K+ in both internal and external solutions to block K+ currents, and F- was added to the internal solution to block Ca2+ current. INa was activated at a voltage threshold of approximately -70 mV, and maximal inward current was obtained at approximately -30 mV (holding potential = -140 mV). The voltage dependence of steady-state INa availability (h infinity) was sigmoidal with half inactivation occurring at -97.3 +/- 1.1 mV and a slope factor of 5.77 +/- 0.10 mV (n = 60). We did not detect any significant differences in these parameters in cells from patients with a variety of disease states, with or without congestive heart failure. The overlap in voltage dependence of h infinity and Na+ conductance suggested the presence of a Na+ "window" current. An inactivation time course was voltage dependent and was fitted best by the sum of two exponentials. The rate of recovery from inactivation also was voltage dependent and fitted by the sum of two exponentials.(ABSTRACT TRUNCATED AT 250 WORDS)
Arteriolar dilation mediated by capsaicin and calcitonin gene-related peptide in rats
Authors: White C. B. , Roberts A. M. , Joshua I. G.
Published: December 2017

In addition to altering vascular tone by stimulating primary afferent nerves and acting through reflex pathways, capsaicin acts locally. We examined effects of topically applied capsaicin on arteriolar diameter in striated muscle and tested the hypothesis that capsaicin can alter microvascular tone by releasing substance P (SP) or calcitonin gene-related peptide (CGRP). In anesthetized rats, the right cremaster muscle was exposed and suspended in a tissue bath filled with a physiological salt solution. Diameters of third-order arterioles were displayed and measured using in vivo video microscopy. In 17 of 20 rats, addition of capsaicin (3 x 10(-7) M) to the bath dilated arterioles (85 +/- 14% above control). Failure of a second administration of capsaicin to produce a sustained dilation in 6 of 7 arterioles that had previously dilated to capsaicin is consistent with the hypothesis that this agent causes depletion of an endogenous vasodilator. Pretreatment with an SP inhibitor did not alter capsaicin-induced dilation. CGRP (1 x 10(-10) to 2 x 10(-8) M) caused dilation similar to that caused by capsaicin. Pretreatment with a CGRP inhibitor to the bath prevented capsaicin-induced dilation, but not constriction. These results suggest that capsaicin can dilate microvessels by releasing CGRP, which can modulate tone.
Intracellular calcium chelator, BAPTA-AM, prevents cocaine-induced ventricular fibrillation
Authors: Billman G. E.
Published: December 2017

Cocaine is a potent cardiac stimulant that can provoke lethal cardiac events, including ventricular fibrillation (VF). The cocaine-induced accumulation of intracellular calcium could contribute significantly to the development of these lethal arrhythmias. To test this hypothesis, VF was induced in 12 mongrel dogs by the combination of cocaine (1.0 mg/kg) and a 2-min coronary occlusion during exercise. This test without cocaine failed to induce arrhythmias. Pretreatment with the intracellular calcium-specific chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM; 1.0 mg/kg iv) prevented VF in 8 of 12 animals (P < 0.001) and delayed the onset of lethal arrhythmias in 3 of the remaining animals. Cocaine induced significant increases in left ventricular (LV) systolic pressure (control 154.7 +/- 8.7, cocaine 167.4 +/- 8.4 mmHg), heart rate (control 195.9 +/- 6.1, cocaine 222.3 +/- 10.6 beats/min), and LV maximum rate of pressure development (dP/dtmax; control 5,251 +/- 317.6, cocaine 6,016 +/- 435.1 mmHg/s). BAPTA-AM attenuated the increase in LV dP/dtmax (BAPTA-AM 4,591 +/- 479.3 mmHg/s) and LV systolic pressure (BAPTA-AM 154.5 +/- 6.8 mmHg). Because vascular muscle relaxation could contribute to the cardioprotection, the cocaine and exercise plus ischemia test was repeated after nitroprusside. The nitroprusside prevented cocaine-induced increases in LV systolic pressure but failed to prevent VF. These data suggest that BAPTA-AM may prevent cocaine-induced VF independently of its vascular actions.
Impulse propagation in the Purkinje system and myocardium of intact dogs
Authors: Ben-Haim S. A. , Cable D. G. , Rath T. E. , Carmen L. , Martins J. B.
Published: December 2017

To characterize Purkinje activation (PA) patterns, we studied 15 alpha-chloralose-anesthetized dogs. During left ventricular basal or apical pacing, PA was mapped with a row of four to eight multipolar electrodes placed in the left ventricular wall to record Purkinje and muscle potentials. PA times increased linearly with distance from the pacing site (r = 0.8, slope 1.8 +/- 0.15 mm/ms, P < 0.05). With a single premature stimulus (S2) delivered from the apical or basal site, delay of PA times was first evident at remote sites (> or = 50 mm) with S1-S2 = 185 +/- 5 (SD) ms, while at peripacing sites (< or = 10 mm), delay was first evident when S1-S2 = 176 +/- 6 ms (Purkinje relative refractory period; P < 0.05). With S2,...S5 such that S1-S2 = S2-S3, and so on, an alternating mode of conduction, both temporally and spatially, occurred. The alternation was due to refractoriness and conduction interactions. With short premature intervals, remote coupling intervals were 30 ms less than the premature intervals. Conduction delay in Purkinje fibers with premature stimuli allowed remote epicardium to be activated by alternate routes. Conduction of constant-rate stimuli in the Purkinje system is relatively uniform. With single premature stimuli, conduction is delayed first remotely from the pacing site, whether apical or basal stimulation was employed. When S1-S2 is less than Purkinje relative refractory period, the usual endocardial-to-epicardial activation sequence is altered. Multiple premature stimuli cause remote coupling intervals to alternate.
Involvement of the "tethered ligand" receptor in thrombin-induced endothelium-mediated relaxations
Authors: Tesfamariam B. , Allen G. T. , Normandin D. , Antonaccio M. J.
Published: December 2017

The mechanisms by which the serine protease, alpha-thrombin, mediates relaxations were examined in isolated dog and pig coronary arteries and dog saphenous veins. In rings of coronary arteries and saphenous veins contracted submaximally with prostaglandin F2 alpha or U46619, alpha-thrombin (0.1-10 nM) caused relaxations that were abolished by treatment with N omega-nitro-L-arginine (L-NNA) or removal of the endothelium, indicating that the relaxations were mediated by endothelium-derived nitric oxide. These relaxations were blocked by the thrombin active site inhibitor, MD-805, indicating the requirement of thrombin's catalytic site to induce the relaxations. The thrombin exosite inhibitor, BMS-180742, decreased the sensitivity to alpha-thrombin without altering maximal relaxations. Indomethacin, a cyclooxygenase inhibitor, had no inhibitory effect on the relaxations caused by alpha-thrombin, indicating that the relaxations were not mediated by cyclooxygenase products. Similar to alpha-thrombin, the thrombin receptor activating peptide (human sequence: SFLLRNP, 1-100 microM) caused relaxations in pig coronary artery and dog saphenous vein but not in dog coronary artery. These relaxations were blocked by L-NNA but not by indomethacin. The results indicate that alpha-thrombin induces endothelium-dependent relaxations by a novel signaling mechanism that involves proteolytic cleavage of the thrombin receptor to expose a new amino terminus that functions as a "tethered peptide ligand" to activate thrombin receptors on the endothelial cells and release nitric oxide.
Arteriolar tone is determined by activity of ATP-sensitive potassium channels
Authors: Jackson W. F.
Published: December 2017

The role of ATP-sensitive potassium channels (KATP) in determining resting arteriolar tone and vasodilator reactivity was assessed in superfused, hamster microcirculatory beds studied via intravital microscopy. Under resting conditions, the selective KATP blocker, glibenclamide, produced concentration-dependent vasoconstriction in both the cheek pouch and the cremaster muscle. Concentration-related constriction of cheek pouch arterioles was also observed with tetrapentylammonium, although this agent appeared to have toxic effects on the microcirculation. Glibenclamide (2 microM) abolished arteriolar vasodilation to cromakalim and pinacidil over a concentration range (10 nM-1 microM) in which these agents are selective KATP agonists and also significantly inhibited adenosine-, carbacyclin-, and isoproterenol-induced vasodilation. In contrast, responses to other vasodilators were not significantly affected [methacholine, forskolin, and dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP)] or only slightly depressed (sodium nitroprusside). Thus the activity of KATP determines, in part, resting arteriolar tone in the hamster. Furthermore, vasodilators like adenosine, beta-adrenergic agonists, and prostacyclin appear to act through these ion channels by a mechanism that may not involve cAMP.
Nitric oxide-induced microvascular permeability alterations: a regulatory role for cGMP
Authors: Kubes P.
Published: December 2017

This study evaluated the physiological effects of compounds that alter guanosine 3',5'-cyclic monophosphate (cGMP) on the increase in vascular protein clearance induced by nitric oxide (NO) synthesis inhibition in the feline small intestine. A lymphatic vessel draining the small bowel was cannulated; vascular protein clearance and intestinal blood flow were measured. N omega-nitro-L-arginine methyl ester (L-NAME), the NO inhibitor, was infused (0.5 mumol/min) into the superior mesenteric artery. Vascular protein clearance increased approximately 4.6-fold, whereas blood flow decreased to 50% of control. Elevation of cGMP by 1) cytosolic guanylate cyclase activation with a NO donor (SIN 1) or 2) a cGMP analogue, 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) completely prevented the rise in microvascular permeability associated with L-NAME. Moreover, these compounds reduced (almost 90%) baseline vascular protein clearance, whereas inhibition of cytosolic guanylate cyclase with methylene blue significantly increased this parameter. Atrial natriuretic factor (ANF) has been reported to increase tissue cGMP levels and microvascular permeability. In this study, ANF did indeed increase intestinal microvascular permeability however this occurred independent of changes in intestinal cGMP levels. These data support a role for cGMP associated with NO-induced microvascular permeability alterations and raise the possibility that ANF has a cGMP-independent effect on microvascular permeability within the intestine.
Pressure-flow characteristics of the coronary collaterals: a model study
Authors: Manor D. , Beyar R. , Sideman S.
Published: December 2017

The pressure-flow relationship of the coronary collaterals is investigated by using an electrical analog model that combines the coronary epicardial arteries with the nonlinear characteristics of the intramyocardial circulation. The study aims to examine some controversial issues concerning the collateral circulation, including the transmural distribution of the collaterals, the distensibility of the collateral vessels (whether rigid or complaint), the effects of microcirculatory embolization, the collateral zero-flow pressure, and the nonlinearity of the collateral pressure-flow relationship. The study is carried out by simulating and comparing two basic experimental set-ups in which a coronary artery is ligated and the retrograde flow serves as an index of collateral flow. In the first “free-flow” setup, flow is allowed to bleed retrogradely against atmospheric pressure while perfusion pressure to the rest of the coronary arteries is varied over a wide range. In the second “back-pressure” setup, the coronary perfusion pressure is maintained at the control levels while the back pressure to the retrograde flow in the excised artery is varied. According to the analysis, the nonlinear pressure-flow relationships depend heavily on the experimental setup and are a function of the distensibility of the collaterals, which are distributed mainly on the epicardial surface, and the nonlinear contraction characteristics of the myocardium. The measured retrograde flow tends to underestimate the total collateral flow for the back-pressure setup because of antegrade flow escape.
Rat vascular tissues express all three alpha-isoforms of Na(+)-K(+)-ATPase
Authors: Sahin-Erdemli I. , Rashed S. M. , Songu-Mize E.
Published: December 2017

The catalytic alpha- and smaller glycosylated beta-subunits of the membrane transport enzyme Na(+)-K(+)-adenosinetriphosphatase (ATPase) occur in different molecular forms, alpha 1, alpha 2, alpha 3, beta 1, and beta 2. The catalytic alpha 1-, alpha 2-, and alpha 3-subunits of the enzyme have varying affinities for digitalis and exist in different tissues with unique distribution patterns. In this report we document for the first time the existence of alpha 1-, alpha 2-, alpha 3-subunit proteins (all approximately 97.5 kDa) in cultured rat aortic smooth muscle cells and rat tail arteries. In addition to the three molecular forms of the alpha-protein we detected a minor band at approximately 68-kDa position in aortic smooth muscle cells, which may correspond to the truncated alpha 1-protein reported earlier.
Ouabain in plasma from spontaneously hypertensive rats
Authors: Doris P. A.
Published: December 2017

Ouabain has recently been identified in mammalian plasma with an apparent adrenocortical origin. The objectives of the present study were to determine whether boiled plasma supernatants (BPS) from spontaneously hypertensive rats (SHR) contained elevated levels of material able to inhibit 86Rb uptake, an indicator of sodium pump activity, compared with Wistar-Kyoto rats (WKY). Furthermore, the effect of increasing dietary calcium content from 1 to 3% on 86Rb-uptake inhibitory activity in plasma was examined. BPS from SHR and WKY consuming 1% calcium contained sodium pump inhibitory activity equivalent to 16.43 +/- 0.23 and 5.08 +/- 0.10 ng ouabain/ml, respectively (P < 0.0001). Increasing dietary calcium intake to 3% reduced plasma ouabain-like activity (OLA) to 9.97 +/- 0.20 ng/ml (P < 0.0001) in SHR but was without effect in WKY (5.39 +/- 0.05; not significant). It was then determined whether the plasma 86Rb-uptake inhibition could be attributed to authentic ouabain. In WKY plasma pools the percentage of OLA attributable to authentic ouabain was 38.0% by radioimmunoassay and 56.7% by 86Rb-uptake assay. In SHR these values were 3.8% and < 7.1%, respectively. Whereas the data in the present study provide confirmation of the presence of ouabain in rat plasma, ouabain does not account for the elevated OLA in SHR plasma reported here and elsewhere. This hypertensinogenic cardiotonic steroid appears to be appropriately downregulated in SHR rats.
Role of sarcoplasmic reticulum in loss of load-sensitive relaxation in pressure overload cardiac hypertrophy
Authors: Cory C. R. , Grange R. W. , Houston M. E.
Published: December 2017

The loss of load-sensitive relaxation observed in the pressure-overloaded heart may reflect a strategy of slowed cytosolic Ca2+ uptake to yield a prolongation of the active state of the muscle and a decrease in cellular energy expenditure. A decrease in the potential of the sarcoplasmic reticulum (SR) to resequester cytosolic Ca2+ during diastole could contribute to this attenuated load sensitivity. To test this hypothesis, both in vitro mechanical function of anterior papillary muscles and the SR Ca2+ sequestration potential of female guinea pig left ventricle were compared in cardiac hypertrophy (Hyp) and sham-operated (Sham) groups. Twenty-one days of pressure overload induced by coarctation of the suprarenal, subdiaphragmatic aorta resulted in a 36% increase in left ventricular mass in the Hyp. Peak isometric tension, the rate of isometric tension development, and the maximal rates of isometric and isotonic relaxation were significantly reduced in Hyp. Load-sensitive relaxation were significantly reduced in Hyp. Load-sensitive relaxation quantified by the ratio of a rapid loading to unloading force step in isotonically contracting papillary muscle was reduced 50% in Hyp muscles. Maximum activity of SR Ca(2+)-adenosinetriphosphatase (ATPase) measured under optimal conditions (37 degrees C; saturating Ca2+) was unaltered, but at low free Ca2+ concentrations (0.65 microM), it was decreased by 43% of the Sham response. Bivariate regression analysis revealed a significant (r = 0.84; P = 0.009) relationship between the decrease in SR Ca(2+)-ATPase activity and the loss of load-sensitive relaxation after aortic coarctation. Stimulation of the SR Ca(2+)-ATPase by the catalytic subunit of adenosine 3',5'-cyclic monophosphate-dependent protein kinase resulted in a 2.6-fold increase for Sham but only a 1.6-fold increase for Hyp. Semiquantitative Western blot radioimmunoassays revealed that the changes in SR Ca(2+)-ATPase activity were not due to decreases in the content of the Ca(2+)-ATPase protein or phospholamban. Our data directly implicate a role for decreased SR function in attenuated load sensitivity. A purposeful downregulation of SR Ca2+ uptake likely results from a qualitative rather than a quantitative change in the ATPase and possibly one of its key regulators, phospholamban.
Peptidases modulate bradykinin-induced arteriolar dilation in the hamster cheek pouch
Authors: Gao X. P. , Anding P. , Robbins R. A. , Rennard S. I. , Rubinstein I.
Published: December 2017

The purpose of this study was to investigate whether angiotensin-converting enzyme (ACE; EC 3.4.15.1) and neutral endopeptidase (NEP; EC 3.4.24.11), two membrane-bound metalloenzymes that are widely distributed in the peripheral microcirculation and degrade kinins very effectively, modulate bradykinin-induced arteriolar dilation in vivo. Using intravital microscopy, we measured diameter of second-order arterioles in the hamster cheek pouch during suffusion of bradykinin (0.1–10.0 microM) before and after topical application of captopril (10.0 microM) and phosphoramidon (10.0 nM). We found that each inhibitor significantly potentiated bradykinin-induced increase in arteriolar diameter (P < 0.05). Suffusion of other proteinase inhibitors (excluding ACE and NEP inhibitors) had no significant effect on bradykinin-induced responses. Captopril and phosphoramidon did not potentiate isoproterenol (0.1 microM)-induced arteriolar dilation in the cheek pouch. Collectively, these data indicate that ACE and NEP each plays an important role in regulating bradykinin-induced vasorelaxation in the peripheral microcirculation in vivo.
Influence of endurance exercise training on distribution of vascular adaptations in rat skeletal muscle
Authors: Sexton W. L. , Laughlin M. H.
Published: December 2017

We hypothesized that an exercise training program consisting of treadmill running at 32 m/min up a 15% incline, 90 min/day, 5 days/wk for 12–14 wk, would elicit vascular adaptation in skeletal muscle of all fiber types in rats. This hypothesis was based on previous reports that this intensity and duration of training caused increases in oxidative capacity in rat skeletal muscle of all fiber types. Skeletal muscle vascular transport capacity was examined with measurements of total and regional (radiolabeled microspheres) flow capacity, capillary filtration coefficient (CFC), and permeability-surface area product (PS) for 51Cr-EDTA in maximally vasodilated (papaverine) hindquarters of control (C; n = 25) and exercise-trained (ET; n = 26) rats. CFC was increased in ET (0.038 +/- 0.001 vs. 0.030 +/- 0.001 ml.min-1 x mmHg-1 x 100 g-1; P < or = 0.001). PS was greater in ET than C (7.80 +/- 0.33 vs. 6.39 +/- 0.37 ml.min-1 x 100 g-1; P < or = 0.01). Citrate synthase activity was increased in the soleus (25%; P < or = 0.05), the medial head (35%; P < or = 0.05), and the red portion of the long head (45%; P < or = 0.005) but not in the white portion of the long head of triceps brachii (P = 0.14) of ET rats. Pressure-flow relationships indicate that total flow was greater (P < or = 0.05) in ET hindquarters at all perfusion pressures. Regional flow data revealed that increases in flow capacity were not evident in muscles composed of all fiber types as predicted.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of R-56865 on transient inward current, Na(+)-Ca2+ exchange, and Ca2+ release from SR in cardiac myocytes
Authors: Ichikawa H. , Hearse D. J. , Coetzee W. A.
Published: December 2017

Voltage-clamp studies were performed on guinea pig ventricular myocytes to clarify the action of N-(1-[4-(4-fluorophenoxy)butyl]-4-piperidinyl)-N-methyl-2-benzothiazo lamine (R-56865), an inhibitor of cardiac glycoside-induced arrhythmias. Transient inward current ((Iti)) was induced using low-K+/high-Ca2+ Tyrode solution. R-56865 (1 mM) was found to abolish I(ti). R-56865 had no influence on the peak Ca2+ current, steady-state current during the clamp, holding current, or the Ni(2+)-sensitive electrogenic Na(+)-Ca2+ exchange current. Fluorescence transients after repolarization (temporally related to the I(ti)) were abolished by R-56865 without affecting the fluorescence transients during depolarization. In separate experiments, the threshold of Ca2+ release from sarcoplasmic reticulum (SR) by the Ca2+ current was found to be unchanged, whereas Ca2+ transients (presumably triggered by Ca2+ entry through the Na(+)-Ca2+ exchanger) were depressed. Our results suggest that R-56865 inhibits spontaneous Ca2+ release from the SR when it is mediated by Ca2+ entry through the Na(+)-Ca2+ exchanger but that it has no direct effect on the well-known “physiological” Ca(2+)-induced Ca(2+)-release mechanism from SR.
Vascular Ca overload produced by vitamin D3 plus nicotine diminishes arterial distensibility in rats
Authors: Atkinson J. , Poitevin P. , Chillon J. M. , Lartaud I. , Levy B.
Published: December 2017

In humans, aging produces many structural changes in blood vessels, one of the most pronounced being arterial calcium overload. Simultaneously arteries become increasingly rigid. The slow evolution of the two processes renders it difficult to evaluate the importance of vascular calcium overload in the development of decreased compliance. To gain insight into this relationship, rapid vascular calcium overload was produced by treating young rats with vitamin D3 and nicotine. When rats were allowed 16 days or longer to recover from such treatment, analysis of plasma parameters revealed no overt toxicity, and growth rate was similar to that of controls. Pronounced calcium overload was seen primarily in compliance arteries. Changes in systemic arterial compliance, characteristic impedance, pulse-wave velocity, and carotid compliance all reflected a substantial increase in arterial rigidity. Linear regression analysis revealed significant correlations between the various indicators of arterial distensibility and arterial calcium content. In conclusion, treatment of young rats with vitamin D3 and nicotine may provide a suitable model with which to investigate how calcium overload is involved in the induration of compliance arteries.
Endocardial and epicardial interstitial purines and lactate during graded ischemia
Authors: Delyani J. A. , Van Wylen D. G.
Published: December 2017

The purpose of this study was to compare interstitial fluid (ISF) levels of purine metabolites and lactate in the endocardium and the epicardium during graded regional myocardial ischemia and reperfusion. Anesthetized dogs were subjected to 60 min of regional myocardial ischemia induced by either partial or complete occlusion of the left anterior descending coronary artery (LAD), followed by 60 min of reperfusion. To sample ISF, cardiac microdialysis probes were implanted in the LAD-perfused myocardium; dialysate levels served as indexes of ISF concentrations. During severe ischemia, dialysate adenosine increased transiently in both the endocardium and epicardium, reaching maximal values at approximately 20 min of ischemia. Inosine, hypoxanthine, xanthine, and lactate increased most rapidly during the first 30 min of severe ischemia, after which the rate of increase was diminished. The ISF profiles of these metabolites were qualitatively similar during moderate ischemia, although the ISF levels achieved during ischemia were not as great. With both severe and moderate ischemia, ISF purines and lactate were greater in the endocardium than epicardium, consistent with a greater energy imbalance in the endocardium during ischemia. ISF total purines (the sum of the individual purine metabolites) were relatively stable until myocardial blood flow was reduced below 50 ml.min-1 x 100 g-1, after which ISF total purines increased in proportion to the severity of the blood flow deficit. These data suggest that functional and metabolic adaptations keep the myocardium in energy balance until blood flow is reduced below approximately 50% of control, and they attest to the usefulness of cardiac microdialysis for establishing transmural profiles of ISF metabolites.
Cerebrovascular autoregulation during fetal development in sheep
Authors: Helou S. , Koehler R. C. , Gleason C. A. , Jones M. D. , Traystman R. J.
Published: December 2017

There are scant data regarding the development of cerebrovascular autoregulation in fetuses. We tested the hypothesis that a decrease in cerebrovascular resistance (CVR) at reduced cerebral perfusion pressure (CPP) is absent in midgestation and near-term fetal sheep. Catheters were chronically implanted for microsphere determination of cerebral blood flow (CBF) in 9 fetuses at 92 days and in 10 fetuses at 132 days gestation (full term = 145 days). CPP was reduced by ventricular infusion of artificial cerebrospinal fluid. In 92-day fetuses, CPP was reduced stepwise from 35 to 25 and 18 mmHg and CBF decreased from 52 +/- 5 to 43 +/- 4 and 27 +/- 5 (SE) ml.min-1 x 100 g-1, respectively. Half of the immature fetuses showed some reduction in CVR at moderate reduction in CPP; however, there was no significant change in CVR in the group as a whole (from 0.72 +/- 0.06 to 0.61 +/- 0.04 and 0.89 +/- 0.20 mmHg.ml-1.min.100 g). In 132-day fetuses, CPP was reduced from 45 to 33 and 28 mmHg and CBF was unchanged (from 105 +/- 7 to 97 +/- 11 and 89 +/- 8 ml.min-1 x 100 g-1). CVR decreased from 0.45 +/- 0.05 to 0.41 +/- 0.08 and 0.33 +/- 0.03 mmHg.ml-1.min.100 g. There were no significant changes in arterial blood gases at reduced CPP in either age group. We conclude that cerebrovascular autoregulation at reduced CPP is not well developed at 92 days (0.63 gestation) in fetal sheep but that autoregulatory capacity is evident near term. We speculate that poor autoregulation may place the premature fetal brain at risk for injury.
Preconditioning protects ischemic rabbit heart by protein kinase C activation
Authors: Ytrehus K. , Liu Y. , Downey J. M.
Published: December 2017

Myocardial protection in the rabbit induced by ischemic preconditioning is thought to be adenosine receptor linked, but the signaling pathway responsible for the protection has yet to be identified. This study tests whether protein kinase C could be involved. Either of two inhibitors of protein kinase C, staurosporine (50 micrograms/kg) or polymyxin B (24 mg/kg), were administered to rabbits subjected to 30 min regional myocardial ischemia followed by 180 min reperfusion. Half of the rabbits were preconditioned while the other half served as nonpreconditioned controls. Nonpreconditioned hearts without drug or treated with staurosporine or polymyxin B resulted in 37.8 +/- 3.1, 40.5 +/- 2.8, and 42.0 +/- 7.0% infarction of the risk zone, respectively. Preconditioning limited infarct size to 7.3 +/- 2.7%. Both inhibitors blocked protection in preconditioned hearts with 36.2 +/- 2.7 and 40.9 +/- 2.5% of the risk zone infarcted, respectively. Activation of protein kinase C with 4 beta-phorbol 12-myristate 13-acetate (PMA) or with 1-oleyl-2-acetyl glycerol (OAG) mimicked preconditioning in buffer-perfused hearts. PMA (0.01 nmol/min) or OAG (10 nmol/min) for 5 min was followed by 10 min of washout. Infarct size after 30 min regional ischemia was limited in the PMA and OAG groups (6.4 +/- 1.4 and 11.7 +/- 3.3 vs. 28.0 +/- 4.5% in untreated controls) and was equipotent with ischemic preconditioning (11.8 +/- 2.2%). Polymyxin B also blocked protection from ischemic preconditioning in the isolated heart (33.0 +/- 5.0%).(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiac hypertrophy in the ferret increases expression of the Na(+)-K(+)-ATPase alpha 1- but not alpha 3-isoform
Authors: Book C. B. , Wilson R. P. , Ng Y. C.
Published: December 2017

Work overload alters expression of the Na(+)-K(+)-adenosinetriphosphatase (ATPase) multigene family in the myocardium. However, due to lack of an appropriate animal model, very little is known regarding regulation of the alpha 3-isoform. We previously reported that adult ferret myocardium expresses the alpha 1- and alpha 3-isoforms of Na(+)-K(+)-ATPase. In the current study we examined the relative abundances of these isoforms in a recently developed ferret model of pressure-overload cardiac hypertrophy. Ferrets with abdominal aortic constriction (Coarc) developed significant left ventricular hypertrophy based on altered morphometric measurements and switching of the myosin heavy chain isoforms. Western and Northern blotting analyses showed that in hypertrophied left ventricles of Coarc ferrets the abundance of alpha 1-protein increased (27%), whereas that of alpha 1-mRNA remained unchanged. In nonhypertrophied right ventricles of Coarc ferrets abundance of alpha 1-protein remained unchanged. Expression of the alpha 3-isoform in left ventricles of Coarc ferrets remained unchanged at both protein and mRNA levels. By contrast, abundance of beta 1-mRNA increased significantly (31%), whereas beta 1-protein remained unchanged. Na(+)-K(+)-ATPase activity, estimated by K(+)-dependent nitrophenyl phosphatase activity, did not differ between left ventricular homogenates from Coarc and sham-operated ferrets. In conclusion, these studies indicate that in hypertrophied ferret heart Na(+)-K(+)-ATPase isoforms are differentially regulated at pretranslational, as well as at translational-posttranslational levels.
Intramyocardial pressure gradients in working and nonworking isolated cat hearts
Authors: Mihailescu L. S. , Abel F. L.
Published: December 2017

This study presents an improved method for the measurement of intramyocardial pressure (IMP) using the servo-nulling mechanism. Glass micropipettes (20-24 microns OD) were used as transducers, coated to increase their mechanical resistance to breakage, and placed inside the left ventricular wall with a micropipette holder and manipulator. IMP was measured at the base of the left ventricle in working and nonworking isolated cat hearts that were perfused with Krebs-Henseleit buffer. In working hearts a transmural gradient of systolic IMP oriented from endocardium toward the epicardium was found; the endocardial values for systolic IMP were slightly higher than systolic left ventricular pressure (LVP), by 11-18%. Increases in afterload induced increases in IMP, without changing the systolic IMP-to-LVP ratio. In nonworking hearts with drained left ventricles, the systolic transmural gradient for IMP described for working hearts persisted, but at lower values, and was directly dependent on coronary perfusion pressure. Systolic IMP-to-LVP ratios were always > 1. The diastolic IMP of both working and nonworking hearts exhibited irregular transmural gradients. Our results support the view that generated systolic IMP is largely independent of LVP development.
Molecular determinants of lipid mediator-induced leukocyte adherence and emigration in rat mesenteric venules
Authors: Zimmerman B. J. , Holt J. W. , Paulson J. C. , Anderson D. C. , Miyasaka M. , Tamatani T. , Todd R. F. , Rusche J. R. , Granger D. N.
Published: December 2017

The objective of this study was to identify the molecular determinants of leukocyte rolling, adherence, and emigration elicited in postcapillary venules by the lipid mediators leukotriene B4 (LTB4) or platelet-activating factor (PAF). Leukocyte-endothelial cell adhesion and shear rate were monitored in rat mesenteric venules during superfusion with either LTB4 or PAF in the presence or absence of monoclonal antibodies (MAbs) directed against either leukocyte (CD18, CD11b) or endothelial cell [intercellular adhesion molecule 1 (ICAM-1), E-selectin, P-selectin] adhesion glycoproteins. In untreated animals and in animals receiving a nonbinding control MAb, LTB4 and PAF increased the number of both adherent (8- and 4-fold, respectively) and emigrated (14- and 8-fold, respectively) leukocytes, while reducing leukocyte rolling velocity (36 and 33%, respectively). The LTB4- and PAF-induced leukocyte adherence and emigration were significantly attenuated by pretreatment with MAbs directed against CD18, CD11b, ICAM-1, and E-selectin, but not P-selectin. The reduction in leukocyte rolling velocity induced by LTB4 was not affected by any of the MAbs; however, both P- and E-selectin MAbs significantly attenuated the reduction in leukocyte rolling velocity elicited by PAF. The results of this study indicate that the leukocyte adherence and emigration induced by both LTB4 and PAF are mediated by CD11b/CD18 on leukocytes and by ICAM-1 and E-selectin on endothelial cells. The molecular determinant of leukocyte rolling appears to be mediator specific, with the selectins mediating the rolling elicited by PAF.
Characterization of endothelin receptors mediating contraction of rabbit saphenous vein
Authors: Gray G. A. , Loffler B. M. , Clozel M.
Published: December 2017

The goal of this study was to characterize endothelin (ET) receptors mediating contraction of the rabbit saphenous vein. For this purpose, binding and functional studies were performed. Two receptor subtypes mediated contraction in response to ET-1. The first, responsible for 80-90% of maximal contraction, was stimulated with equal potency by ET-1, ET-3, and sarafotoxin S6c. The second, responsible for the remaining contraction, was stimulated more potently by ET-1 than by ET-3 and not by sarafotoxin S6c. The specific ETA receptor antagonist BQ-123 and the inhibitor of protein kinase C (PKC) Ro 31-8220 inhibited ET-1 contraction via the second but not the first receptor. In plasma membranes 125I-labeled ET-1 bound predominantly to a site with characteristics of ETA receptor, whereas 125I-ET-3 bound to two sites with characteristics of ETB receptor, one of high and one of low affinity. Comparison of binding affinity constants and 50% effective concentrations shows that the high-affinity ETB receptor corresponds to the receptor mediating the major part of contraction independently of PKC activation and ETA to the receptor mediating the minor part of contraction via a PKC-dependent mechanism.
Vascular effects of 17 beta-estradiol in male Sprague-Dawley rats
Authors: Shan J. , Resnick L. M. , Liu Q. Y. , Wu X. C. , Barbagallo M. , Pang P. K.
Published: December 2017

Bolus intravenous injections of 100 micrograms/kg 17 beta-estradiol significantly decreased the pressor responses to norepinephrine (NE; 0.3 microgram/kg) at the fourth, fifth, and sixth hour in anesthetized male Sprague-Dawley rats. At doses of 10(-6) to 3 x 10(-5) M, 17 beta-estradiol relaxed the sustained phase of contraction in male Sprague-Dawley rat tail artery helical strips precontracted in vitro by [Arg8]vasopressin (AVP), KCl, or NE. The effect was dose dependent. At doses of 3 x 10(-6) to 3 x 10(-5) M, it also decreased the initial phase of tension generation and extracellular Ca(2+)-dependent vasoconstriction induced by NE, AVP, or KCl in a dose-dependent manner in male Sprague-Dawley rat tail artery helical strips. 17 beta-Estradiol (2 x 10(-8) to 2 x 10(-6) M) decreased the voltage-dependent inward Ca2+ current and the intracellular free Ca2+ concentration ([Ca2+]i) increment induced by 15 mM KCl in a dose-dependent manner (3.6 x 10(-8) to 3.6 x 10(-6) M) in vascular smooth muscle cells (VSMC) isolated from male Sprague-Dawley rat tail arteries. We suggest that, at pharmacological doses, estrogen has a direct vasodilating effect on the rat tail artery that is mediated by its inhibitory effect on Ca2+ influx through voltage-dependent Ca2+ channels. The inhibitory effect of estrogen on the pressor responses to NE or AVP may be correlated with its modulation of VSMC [Ca2+]i through its actions on membrane Ca2+ channels.
Blood-brain barrier permeability measurements by double-indicator method using intravenous injection
Authors: Knudsen G. M. , Pettigrew K. D. , Patlak C. S. , Paulson O. B.
Published: December 2017

The double-indicator technique with intracarotid bolus injection is useful for the estimation of transfer rates across the human blood-brain barrier. A method using intravenous tracer injection is developed whereby the input is measured at a peripheral artery and the output is measured at the jugular vein. To correct for differences in the brain input of test and reference substances, a five-parameter Dirac impulse response for passage through the cerebrovascular bed is computed from the input and output of the reference substance. This response is then combined with a capillary model of the brain. This is then convoluted with the arterial input curve of the test substance to yield a theoretical test output curve, which is compared with the actual test output curve. On the basis of these two curves and an appropriate mathematical model for the brain, estimates of blood-brain barrier permeability are obtained. In the present study, the techniques are compared in 13 patients in whom alternating intracarotid and intravenous bolus injections were given. For D-glucose, the two techniques yielded similar results. This was also the case for L-phenylalanine, provided that the erythrocyte compartment was taken into account. Data obtained after intravenous injection of leucine and water yielded similar results compared with previous intracarotid data.
The effect of fetal lung inflation on fetal heart rate
Authors: Nail B. S. , Lumbers E. R. , Stevens A. D.
Published: December 2017

The effect on the fetal heart by inflating the fetal lungs with liquid or air while the animal was being maintained in utero by its normal placental circulation was investigated in 10 healthy, chronically catheterized fetal sheep of gestational age 126-137 days. It was found that initial attempts to inflate the lungs with volumes of air as small as 10 ml (i.e., with less than a predicted normal tidal volume) caused abrupt, powerful slowing of the fetal heart with, usually, an associated hypotension. Inflations with similarly small volumes of saline were ineffective. Atropine pretreatment abolished the cardiac slowing caused by the air inflations, indicating the operation of a neural reflex. An analysis of the pressure changes induced by the air and liquid inflations in airway, intrathoracic and intra-amniotic pressures showed that the cardiac slowing was primarily related to the level of mechanical stress applied across the fetal airway.
Depolarization-induced Ca entry via Na-Ca exchange triggers SR release in guinea pig cardiac myocytes
Authors: Levi A. J. , Spitzer K. W. , Kohmoto O. , Bridge J. H.
Published: December 2017

In mammalian heart muscle, Ca entry through L-type Ca channels is thought to be the primary trigger for the sarcoplasmic reticulum (SR) Ca release, which initiates contraction. The results of this study show that, in guinea pig myocytes with a normal internal Na (10 mM Na in pipette), another trigger mechanisms for SR release and contraction exists. A crucial feature of these experiments was the ability to change rapidly the extracellular environment of a single myocyte so that alterations of intracellular Ca and SR Ca load were minimized for each solution change. We found the following results. 1) A switch to Na-free solution 50 ms before depolarization led to an increase of phasic contraction without increasing L-type Ca current (Ica) or Ca loading of the SR. 2) Although rapid application of 20 microM nifedipine 3 s before a + 10-mV pulse blocked ICa completely, 43 +/- 11 (SE) % of the phasic contraction remained. Similar results were obtained by rapid switching to 150 microM Cd to block ICa. 3) Phasic contraction and ICa had different voltage dependence. With steps to positive potentials there was little ICa but still a substantial phasic contraction. 4) Under action potential conditions, 64.6 +/- 7.9% of the control phasic contraction remained after switching to 20 microM nifedipine to block ICa. 5) The contraction remaining with nifedipine was unaffected by adding 100 microM Ni. Because 100 microM Ni blocks T-type Ca channels, this shows that Ca entry via T-type Ca channels is not involved in triggering SR release. 6) The phasic contraction remaining after a rapid switch to nifedipine was blocked completely by adding 5 mM Ni. Because this concentration of Ni is known to block the Na-Ca exchange, this result suggests that the exchange plays a role in triggering SR release. Taken together, the present results indicate that depolarization-induced Ca entry on the Na-Ca exchange is able to trigger SR release and phasic contraction. This explanation can account for increased phasic contraction after a rapid switch to Na-free solution, persistence of a phasic contraction in the complete absence of ICa, substantial phasic contraction at positive test potentials where there is no ICa, and abolition of nifedipine-resistant contraction by 5 mM Ni.