bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Chronic Denervation on the Activities of Monoamine Oxidase and Catechol-O-Methyl Transferase and on the Contents of Noradrenaline and Adenosine Triphosphate in the Rabbit Ear Artery
Authors: Head R.J. , Stitzel R.E. , de la Lande I.S. , Johnson S.M.
Published: September 2008

When assayed on homogenates of the rabbit ear artery up to 192 h after sympathetic denervation, the activity of monoamine oxidase (MAO) showed a small but significant decrease (maximum 9%). The activity of catechol-O-methyl transferase (COMT) appeared unchanged, although it is possible that the small and variable nature of this enzyme activity compared with that of MAO may have masked a comparable effect of denervation. The maximum decreases in noradrenaline (NA) and adenosine triphosphate (ATP) contents were >90% at 48 h, and 32% at 96 h after denervation. These results confirm the presence of neuronal as well as extraneuronal MAO, and also the presence of extraneuronal COMT in this artery. The decline in ATP contents after denervation suggest that part of the ATP is neuronal. However, the estimated ratio of NA to neuronal ATP is far in excess of that reported for isolated noradrenaline storage vesicles, suggesting that the major portion of the neuronal ATP was not present in these vesicles.
Response of Blood Vessels to Sympathetic Nerve Stimulation
Authors: Bevan J.A.
Published: September 2008

The frequency response curves (FRC) of isolated blood vessels differ from each other not only in their initial slopes, but in their maxima, and their intercept on the frequency axis. Within the physiological range, there is a linear relation between response and frequency. The FRC of most vessels with junctional innervation are similar, varying only somewhat with innervation density. Other factors found to influence the FRC are: variation in innervation distribution, in the extent of myogenic propagation, and large differences in the sensitivity of the α-adrenergic receptor. The effectiveness of the transmitter increases with frequency rise. The maximum effective radius of the transmitter released from one varicosity is only several microns. In vessels with light to moderate innervation density at low frequencies, there is probably little overlap of transmitter effect from adjacent varicosities even at the outermost layers of smooth muscle cells. There is a disparity between neurogenic response and that which might be expected from the direct action of the transmitter. It is proposed that a local limited myogenic extension of excitation may extend the local action of a quantum of transmitter.
Estimate of Cellular Force Generation in an Arterial Smooth Muscle with a High Actin: Myosin Ratio
Authors: Driska S.P. , Murphy R.A.
Published: September 2008

An in vitro preparation from the media of the pig carotid artery develops somewhat higher force/cell cross-sectional area with one-fifth the myosin content of skeletal muscle cells. The following results suggest that this performance reflects cellular properties rather than the arrangement of cells within the tissue: (1) force development at the peak of the length-force curve is independent of the length of the tissue segment in a strip of constant cross-section, and (2) average cell length is directly proportional to tissue length. We conclude that the contractile system of arterial smooth muscle cells is specialized for force generation and that the mechanical properties of the pig carotid media preparation provide valid estimates of cellular function.
Relationship between Noradrenaline-Induced Depolarization and Contraction in Vascular Smooth Muscle
Authors: Haeusler Guenther
Published: September 2008

In strips of rabbit main pulmonary artery, full dose-response curves of noradrenaline for the mechanical and electrical responses of the vascular smooth muscle cells were obtained under normal conditions and after increasing and decreasing the membrane potential with strychnine and tetraethylammonium, respectively. The results suggest that the magnitude of the noradrenaline-induced contraction is related to the height of the membrane potential and not to the degree of depolarization produced by the adrenergic transmitter.
Involvement of Calcium in Cyclic Nucleotide Metabolism in Human Vascular Smooth Muscle
Authors: Hidaka Hiroyoshi , Yamaki Tokuo , Asano Masahisa , Totsuka Tsuyoshi
Published: September 2008

When cyclic nucleotide phosphodiesterase was purified from isolated smooth muscle layer of human aorta by DEAE-cellulose column chromatography, separated cyclic GMP phosphodiesterase activity was markedly stimulated in the presence of 10–20 µM of Ca2+ by a protein modulator which has similar physico-chemical properties to troponin C. Synthetic compound, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, which produced relaxations of arteries contracted by prostaglandin F2α or KCl was found to inhibit selectively this Ca2+-dependent cyclic GMP phosphodiesterase. This compound produced inhibition of superprecipitation of myosin B system obtained form mouse skeletal muscle and also inhibited adenosine triphosphatase activity of myosin B. Our data suggest that calcium is involved through a protein modulator in cyclic nucleotide metabolism of vascular smooth muscle and that the calcium-dependent protein modulator probably participates in the regulation of contractile response of vascular smooth muscle by affecting actomyosin ATPase activity.
Ion Transport in Tonic and Phasic Vascular Smooth Muscle and Changes during Deoxycorticosterone Hypertension
Authors: Jones Allan W. , Miller Louis A.
Published: September 2008

The washout of radioisotopes was studied in aorta, femoral artery and portal mesenteric vein from controls and rats made hypertensive with injection of deoxycorticosterone (DOC) acetate. Experiments were also conducted on tonic (pulmonary artery) and phasic (portal mesenteric vein) smooth muscle from rabbits. The rate constants for the washout of 42K, 36Cl and 24Na from aorta were significantly elevated in the DOC hypertensives. Acute removal of extracellular K slowed the washout of 24Na by 50%, however, the rate constant for the DOC group remained higher than the controls. Increased turnover of 42K was also observed in the femoral artery and in a vessel (portal mesenteric vein) not exposed to the effects of high blood pressure in the rat. The rate constants for the washout of 42K, 36Cl and 24Na from phasic smooth muscle in rabbit were greater than the tonic type. Ouabain significantly slowed 24Na washout, however, the rate constant for the portal mesenteric vein remained higher than the pulmonary artery. DOC hypertension was associated with increased ion transport at several vascular sites. A similar change was observed for the phasic vascular smooth muscle from normal rabbits. A question is raised whether increased spontaneous activity of arteries reported to accompany DOC hypertension is the consequence of a membrane in transition from tonic to phasic behavior.
Mechanisms by Which Smooth Muscle Sensitivity May Be Altered by Calcium
Authors: Kaiman Marvin , Shibata Shoji
Published: September 2008

6-Hydroxydopamine (6-OHDA) increased the sensitivity of rat, rabbit and guinea pig portal veins to norepinephrine (NE), methoxamine (ME), barium (Ba++) and calcium (Ca++) but not to potassium (K+). Reserpine potentiated the responses of NE, ME and Ca++ but not Ba++ or K+ in rabbit and guinea pig veins and did not alter the sensitivity of rat veins to all agonists tested. Cocaine only potentiated the NE responses of the veins and decreased the sensitivity of rabbit and guinea pig veins to K+. 6-OHDA increased 45Ca-influx in all veins whereas reserpine increased 45Ca-influx only in rabbit and guinea pig veins. Cocaine failed to increase 45Ca-influx in all veins tested. NE, ME and K+ increased 45Ca-influx in the veins from the different animals. The agonist-induced 45Ca-influx was greater in most of the supersensitive veins than in the control veins. In veins that failed to develop supersensitivity, agonist-induced 45Ca-influx did not differ from that of the control veins. It is concluded that the development of super- and subsensitivity exhibits species variation and that the alteration in Ca++ influx would be consistent with the changes in sensitivity of the venous smooth muscle.
Smooth Muscle Cells in the Development of Plasmatic Arterionecrosis, Arteriosclerosis, and Arterial Contraction
Authors: Ooneda Genju , Yoshida Yoji , Suzuki Keiji , Shinkai Hiroko , Hori Sadao , Kobori Kiyohisa , Takayama Yasuo , Sekiguchi Morie
Published: September 2008

Plasmatic arterionecrosis, the causative lesion of hypertensive cerebral hemorrhage, follows upon medial muscle cell necrosis. The development of medial muscle cell necrosis, the earliest cerebral arterial change seen in hypertensive rats, was inhibited when these animals were fed a cholesterol and lard-supplemented diet. Insudation of fibrin was noted in the arterial intima of hypertensive rats with bilaterally constricted renal arteries. Removal of the constriction induced a fall in the elevated blood pressure and an increase of intimal muscle cells. These were responsible for the dissolution of the deposited fibrin, leading to arteriosclerosis. These myointimal cells may originate from the endothelium. Arterial contraction caused by methoxamine hydrochloride often induced the intrusion of one medial muscle cell into another and increased endothelial permeability. 12–24 h after contraction, the arterial segments showed medial muscle cell necrosis, endothelial desquamation with platelet adhesion, and blood plasma infiltration.
Increased Vascular Collagen Biosynthesis by Hypertension and Reversal by Antihypertensive Drugs
Authors: Spector S. , Ooshima A. , Iwatsuki K. , Fuller G. , Cardinale G. , Udenfriend S.
Published: September 2008

Collagen synthesis was increased in aortas, mesenteric arteries, cerebral microvessels, pial artery, basilar artery and decreased in the heart of rats made hypertensive with deoxycorticosterone acetate-salt or the spontaneously hypertensive animal. The markers of collagen biosynthesis that were elevated were prolyl hydroxylase, prolyl hydroxylase-related antigen, total collagen content and the incorporation of labelled proline into total protein and into collagen. The antihypertensive drugs reserpine and chlorthiazide could both prevent the increase or reduce the increase in collagen synthesis.
Modes of Vasoconstrictor and Vasodilator Neurotransmission
Authors: Su C.
Published: September 2008

Vasoconstrictor and vasodilator neuroeffector transmission occurs in a variety of modes. Models are presented depicting vascular segments under the direct control of a single or multiple innervation, or an indirect influence via secondary release of a vasoactive substance. The neuroeffector relationship in the rabbit portal vein is described to illustrate the coexistence of several modes of transmission. ATP or its congener is released from the nonadrenergic vasodilator nerves in this vein, possibly as the transmitter. Further, a similar substance is released from the adrenergic vasoconstrictor nerves. It possibly acts directly on smooth muscle cells to relax them, and on the nerve terminals to inhibit the adrenergic transmitter release. Evidence suggests that such purine-mediated feedback mechanism may also occur at many other adrenergic and nonadrenergic neuroeffector synapses.
Potassium-Induced Relaxation as an Indicator of Na+-K+ ATPase Activity in Vascular Smooth Muscle
Authors: Webb Clinton , Bohr David F.
Published: September 2008

Helical strips of rat tail artery were observed to relax in response to potassium after contraction induced by 10–7 g/ml norepinephrine in potassium-free solution. After several minutes of relaxation, the strips showed an abrupt redevelopment of tension. The amplitude of the potassium-induced relaxation was employed as an index of the activity of the electrogenic sodium-potassium pump and hence of the Na+-K+ ATPase. This assumption seemed justified because the observed amplitude of potassium-induced relaxation paralleled known effects of the following variables on Na+-K+ ATPase: (1) intracellular sodium concentration; (2) ouabain administration; (3) magnesium; (4) temperature, and (5) potassium concentration. The relaxation that occurred in response to potassium is suggested to be due to an enhanced Na+-K+ ATPase resulting in increased electrogenic transport of sodium and potassium and, consequently, hyperpolarization. We propose that potassium-induced relaxation of rat tail artery may be used as a functional indicator of Na+-K+ ATPase activity in vascular smooth muscle.
Suppression of the Desquamating Effect of Smoking on the Human Endothelium by Hydroxyethylrutosides
Authors: Přerovský I. , Hladovec J.
Published: September 2008

In a group of volunteers, smoking two cigarettes produced a significant increase in the number of circulating endothelial cells. This effect was suppressed in another group by a preventive oral administration of a hydroxyethylrutoside preparation. The results fully confirmed our earlier experimental findings in rats.
Evidence for the Conversion of Angiotensin I to Angiotensin II by the Coronary Microcirculation
Authors: Cornish Kurtis G. , Joyner William L. , Gilmore Joseph P.
Published: September 2008

Cardiac tissue from hamster neonates was transplanted into the hamster cheek pouch. After vascularization of the transplanted tissue the vessels were tested for their ability to convert angiotensin I (AI) to angiotensin II (AII). AI caused vasoconstriction of the coronary vessels which was reduced significantly by converting enzyme inhibitor and the AII antagonist (Sar1-Ala8) angiotensin II. It was concluded that the vessels of transplanted cardiac allografts convert AI to AII in a manner similar to that observed in the whole heart indicating that this procedure provides a good model for studying the microcirculation of the heart.
Increased Reactivity of Isolated Rabbit Saphenous Vein after Treatment with Estrogen and Progesterone
Authors: Rorie Duane K. , Muldoon Sheila M.
Published: September 2008

The effect of estrogen and progesterone on the reactivity of isolated rabbit saphenous veins to adrenergic stimulation by norepinephrine, methoxamine, phenylephrine, and electrical stimulation and the effect of progesterone on the reactivity to barium ions were studied. 8 days after ovariectomy, a saphenous vein was removed and studied in vitro. After 1 and 4 days of hormone therapy, the contralateral vein was removed and its reactivity was compared with that of the first vein and with that of veins from untreated, sham-operated control animals. The reactivity to adrenergic and nonadrenergic stimulation was increased after 4 days of treatment with progesterone (5 mg/day); treatment for 4 days with estrogen (100 µg/day) increased the reactivity to norepinephrine, electrical stimulation, methoxamine, and phenylephrine. The results with progesterone suggest that the increased adrenergic responsiveness is not related to a mechanism controlling adrenergic transmission in veins.
Abnormal Biochemistry of Vascular Smooth Muscle Plasma Membrane as an Important Factor in the Initiation and Maintenance of Hypertension in Rats
Authors: Kwan C.-Y. , Belbeck L. , Daniel E.E.
Published: September 2008

Tissue wet weight as well as total protein content, 5’-nucleotidase activity, alkaline phosphatase activity and Ca2+ accumulation associated with a plasma membrane fraction isolated from spontaneous hypertensive rats (SHR) and rats with deoxycorticosterone (DOC) induced hypertension were investigated. Enhanced alkaline phosphatase activity and reduced ATP-dependent Ca2+ accumulation preceded the development of hypertension in SHR and these effects were reversed by DOC withdrawal followed by lowering of blood pressure in DOC hypertension. Increased arterial tissue wet weight and 5’-nucleotidase occurred only at the later stage of hypertension in SHR and the increased tissue wet weight was not reversed by DOC withdrawal in DOC hypertension. These observations suggest that enhanced alkaline phosphatase and reduced ATP-dependent Ca2+ uptake may play a significant role in initiating hypertension, while increased arterial wet weight and 5’-nucleotidase activities may participate in the maintenance of hypertension.
Adult Microvascular Disturbances as a Result of Juvenile Onset Diabetes in Db/Db Mice
Authors: Bohlen Glenn , Niggl Barbara A.
Published: September 2008

The arterioles in the cremaster muscle of 8 to 10-week-old Ob/Ob, Db/Db and stroptozotocin diabetic mice are characterized by a decreased number of arterioles, loss of vascular tone and a reduced cross-sectional area of the vessel walls. The present study was designed to determine if these abnormalities persist to adult life or if additional abnormalities develop to cause vascular dysfunction. The diameters, wall thickness to lumen ratios and vessel wall areas of comparable types of innervated arterioles in 24- to 28-week-old normal and Db/Db mice are equivalent, except that the smallest arterioles of Db/Db have thin vessel walls. However, blood flow at rest is only 3.0 ± 0.9 ml/min/100 g of cremasteric muscle tissue in Db/Db mice as compared to 5.5 ± 1.3 ml/min/100 g in normal mice. After all vascular control is abolished, the arterioles of Db/Db dilated, but significantly (p < 0.05) less than in normal animals. The minimum distance between adjacent capillaries (wall to wall) during the passive state was 28 ± 1.7 µm in Db/Db mice and 21.8 ± 0.6 µm in normal mice; this indicates a major decrease of vascularity in the adult Db/Db mouse. The results obtained indicate that the reduction in numbers of arterioles and loss of vascular tone in juvenile diabetic mice persists to adult life but arteriolar wall characteristics become normal in adult life.
Effect of Ionophore RO 2–2985 on the Contractile Response of Canine Coronary, Renal and Femoral Arteries
Authors: Bukoski R.D. , Seidel C.L. , Allen J.C.
Published: September 2008

The effects of the ionophore, RO 2-2985 (X537A, RO) were studied on isolated coronary, renal and femoral arteries in two types of experiments: (l) the effect of RO as a modulator of various contractile effects of KCl and phenylephrine (PE), and (2) the effect of RO itself as a contractile agonist. The effect of the ionophore A23187 was observed in similar experiments to help determine the nature of the RO response. In the first type of experiment, RO was found to have a differential effect upon the arteries contracted with KCl. The coronary arteries relaxed upon addition of the ionophore, whereas, the femoral and renal arteries did not. A23187 had only a transient effect on KCl-contracted coronary arteries. RO relaxed femoral and renal arteries contracted with PE, and A23 187 had only a transient effect. RO attenuated ED50 values and maximum tension developments to both KCl and PE, and A23187 had no effect on these parameters. In the second type of experiment, RO (only at 10–5M) was found to contract femoral and coronary arteries, but had no effect on renal arteries. Experiments with α-blocking agents and calculations using association constants of RO for catecholamines suggest that RO is not acting via catecholamine chelation. The dissimilarity between the effects of RO and A23187 suggest that RO may not be working through a specific effect on Ca++. These differential responses to RO suggest variations in intervessel regulation of PE- and KCl-induced contractions and can explain, in part, the in vivo effects of RO on regional blood flow.
Excitability and NADH Fluorescence of Spontaneously Active Portal Veins in Relation to Glucose Withdrawal
Authors: Linke A.M. , Betz E.
Published: September 2008

The effect of glucose withdrawal upon mechanical activity and the redox level of pyridine nucleotides and flavoproteins was investigated in isolated rat portal veins under aerobic conditions. A decrease of extracellular glucose concentration correlated with contractile activity. During acetylcholine-induced tetanic contractions, NADH and flavoproteins were oxydized only in vessels supplied with glucose. The myogenic activity was restituted when glucose was added after withdrawal parallel with a reduction of NAD and flavoproteins. The results suggest that glucose, besides its effect on the energy metabolism, has an influence on the excitability of smooth muscle cells of rat portal veins.
Effect of Adenosine on Adrenergic Neurotransmission in the Superfused Rat Portal Vein
Authors: Moylan Robert D. , Westfall Thomas C.
Published: September 2008

This study examined the effect of exogenously applied adenosine on the release of 3H-norepinephrine from the field-stimulated, superfused rat portal vein. Adenosine was found to inhibit the field-stimulated release of 3H-norepinephrine in a dose-dependent manner in 50- to 1,000-µM concentrations. The effect was reversed when adenosine was washed out. The inhibitory effects of adenosine were antagonized by theophylline (10–4M) which by itself showed a slight enhancement of stimulated 3H-norepinephrine release. ATP was found to inhibit 3H-norepinephrine release at the same concentration as adenosine while inosine was inactive. When adenosine was tested in the presence of the muscarinic and α-adrenergic blocking agents atropine and phenoxybenzamine along with indomethacin, a prostaglandin synthesis inhibitor, its inhibitory effect on the stimulated release of 3H-norepinephrine persisted. It is concluded that adenosine and/or ATP can modulate the nerve-stimulated induced release of norepinephrine presumably by an action on the adrenergic nerve terminals.
Contractile and Morphological Properties of the Portal Vein in Spontaneously Hypertensive and Wistar-Kyoto Rats
Authors: Mulvany M.J. , Ljung B. , Stoltze M. , Kjellstedt A.
Published: September 2008

In perfusion experiments, previous investigations have shown an increased responsiveness of isolated vascular beds from spontaneously hypertensive rats (SHRs) compared with Wistar-Kyoto controls (WKYs). The results have suggested that there are differences in the arterial vessels but not in the venous vessels. Here we have tested the latter part of this hypothesis by comparing the contractile and morphological properties of isolated portal veins from 18 SHRs and 18 WKYs, all 3–4 months old. We found no differences between these veins as regards: (a) maximum force response; (b) active and passive force–length relationship; (c) sensivity to exogenous noradrenaline without and with inhibition of neuronal uptake by cocaine, and (d) cross-sectional area of the longitudinal smooth muscle layer. There was, however, evidence for difference at the cellular level, for the active force per unit cell area was 17% lower in the SHR vessels compared with that in the WKY vessels. With this exception, the results indicate that the morphological and functional differences which have been reported by others for arterial vessels from SHRs and WKYs do not prevail in the portal vein taken from rats at 3–4 months of age.
Potassium and Hydrogen Ion Interaction in the Vasculature of the Isolated, Perfused Guinea Pig Heart
Authors: Young Mark A. , Merrill Gary F.
Published: September 2008

Potassium and hydrogen ion interactions have been reported in the pial vessels of the cerebral vasculature. Adenosine and hydrogen ion interactions were also found in the coronary circulation. We now report an interaction of perfusate pH and potassium in the coronary vasculature. Isolated, perfused guinea pig hearts were used to investigate the possible influence of perfusate pH on hyperkalemic vasodilation and on ouabain blockade of the coronary response to hyperkalemia. At perfusate pH 7.45, potassium infusion increased coronary diastolic flow 18%. At pH 7.21, the same concentration of potassium increased flow 35% above control. The coronary vascular response to potassium was modestly diminished at pH 7.65. The duration of the transient vasodilatory response to potassium at low pH was more than doubled relative to pH 7.45. The presence of ouabain in the perfusate significantly (p < 0.05) reduced the dilating action of potassium at pH 7.01 and 7.65. We conclude that the effect of hyperkalemia on coronary flow is pH sensitive but that ouabain blockade of the potassium response is not effected by changes in pH.
Effects of Antihypertensive Drug Therapy on the Morphology and Mechanics of Resistance Arteries from Spontaneously Hypertensive Rats
Authors: Warshaw D.M. , Root D.T. , Halpern W.
Published: September 2008

Spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY), 25 weeks of age, were treated for 23 weeks with hydrochlorothiazide, hydralazine, and reserpine added to their drinking water. Cylindrical segments of mesenteric arteries (about 170 µm diameter, and 0.7 mm long) were isolated and mounted in a myograph for dimensional and circumferential tension measurements. Treatment of the SHR and WKY decreased systolic blood pressures by 29% and the smooth muscle cell (SMC) content of these vessels by 31%. A linear relation was found between blood pressure and SMC content for all treated and untreated rats. Our results suggest that effect of treatment on the cellular content of the media was sufficient to account entirely for the maintenance of the lowered blood pressure.
Arterial Glycosaminoglycans in Diabetic Dogs
Authors: Sirek O.V. , Sirek A. , Cukerman E.
Published: September 2008

The glycosaminoglycan (GAG) composition of a number of large and medium-sized arteries was studied in 6 alloxan-diabetic beagles and was compared with 6 normal, age-matched controls. Diabetic animals were maintained on diet and insulin for 100 days. The aortic arch, thoracic and abdominal segments, external iliac, superior mesenteric, renal, common carotid and coronary arteries were analyzed for hyaluronic acid (HA) and for heparan (HS), dermatan (DS), and chondroitin (CS) sulphates. All diabetic dogs displayed significant alterations. The HA content was reduced in iliac arteries, and together with HS, also in the thoracic aorta. HS or CS were increased in carotid, iliac and renal arteries, DS, a GAG constituent with very high affinity for low density lipoproteins, was significantly increased in coronary arteries alone. 2 additional animals which are excluded from this series did not become diabetic after alloxanization and showed no change in arterial GAG content. Early changes in the chemistry of the arterial ground substance seem to provide a clue to the precocious development of atherosclerotic disease in diabetes.
Orientation of Arterial Smooth Muscle and Strength of Contraction of Aortic Strips from DOCA-Hypertensive Rats
Authors: Hansen Timothy R. , Dineen Dennis X. , Pullen Gordon L.
Published: September 2008

The functional orientation of vascular smooth muscle in the walls of aortae of DOCA-hypertensive and normotensive rats was determined by measuring the maximum force-generating capacity of strips cut at various angles from their aortae. The greatest tension produced by strips of aortae of either group was generated by strips cut perpendicular to the long axis of the artery. Strips of aortae from either group produced less tension if cut at different angles with respect to the circumferential axis. Cut at any angle, the strips of aorta from DOCA-hypertensive rats produced less tension than those from control rats at the same preload. In length-active stress studies, stress developed by strips cut from DOCA-hypertensive rats was less than that of control rats throughout the entire range of resting lengths. Stereologic analysis of histologic sections of aortae demonstrated a decrease in the volume fraction of smooth muscle in the media of aortic wall. No differences between the carotid arteries of the same DOCA-hypertensive and normotensive rats were found in the proportion of water (by weight) in their walls.
Distribution and Localization of Adenosine 3’:5’-Monophosphate-Dependent Protein Kinase in Mammalian Artery
Authors: Singh Diwan
Published: September 2008

Among the three major vascular layers (the intima-inner, the media-middle smooth muscle, and the adventitia-outer connective tissue) over 90% of the total protein kinase activity was observed in the middle layer. Of various subcellular fractions of the vascular smooth muscle, the 105,000 g supernatant (cytosol fraction) showed the highest specific activity and represented more than two thirds of the total kinase present in this layer. DEAE-cellulose chromatography of the soluble enzyme revealed the existence of two major forms of cyclic AMP-dependent protein kinase, type I and type II, of which 60% of the total enzymatic activity was found in type II. A divalent cation was found to be essential for their phosphotransferase activity. Only Mg2+ and Co2+, but not Zn2+, Mn2+ or Ca2+ could satisfy the cation requirement. The phosphorylated substrate had the characteristics of a protein with a phosphoester bond.
The Influence of Concurrently Administered Theophylline, Ouabain and Hypocapnia on Coronary Flow Perturbations in the Perfused Guinea Pig Heart
Authors: Merrill Gary F. , Young Mark A.
Published: September 2008

Adenosine, potassium ions and hydrogen ions are known to be vasoactive in the coronary circulation. Little is known, however, about the combined effects of these chemicals during reactive hyperemia, flow autoregulation or hypoxic hyperemia. Isolated, perfused guinea pig hearts were used to study the influence of simultaneously administered theophylline, ouabain and alkalosis on coronary flow responses (occlusive hyperemia, autoregulation, hypoxic hyperemia) thought to be contributed to by the above chemicals. Retrograde aortic inflow was monitored electromagnetically in the absence and presence of concurrently administered theophylline (5 × 10–5M), ouabain (1.4 X 10–7M), and alkalosis (perfusate pH 7.69). Upon release of a 30-sec inflow occlusion (in the presence of the above agents) mean peak coronary flow was modestly, but significantly, reduced. Volume flow rate and time for flow to return 50% towards control were reduced in the presence of the above agents, but failed to return to pre-experimental values upon removal of blockers. When perfusion pressure was increased from 65 to 95 cm H2O (antagonists present), coronary myogenic autoregulation was significantly enhanced. Upon decreasing pressure from 95 to 35 cm H2O, in the presence of blockers, calculated coronary resistance fell from 13 ± 0.6 to 9.5 ± 0.5 cm H2O/ml/min. The latter value was significantly higher than that seen in the absence of test agents. No difference in the maximum mean coronary flow achieved by hypoxia (20% O2–5% Co2-balance N2) was seen in the absence or presence of blockers. In conclusion, these experiments provide some indirect support for the involvement of the above metabolites in reactive hyperemia and as antagonists of myogenic blood flow autoregulation. Little evidence for their involvement in hypoxic hyperemia is available from this study.
Vasodilatation Augments the Blood-Brain Barrier Lesions Induced by an Acute Rise in Intracarotid Pressure
Authors: Hardebo J.E.
Published: September 2008

The vessel wall tension is the product of pressure and internal radius divided by the vessel wall thickness. Hence, dilated vessels will be exposed to higher tension at a given intraluminal pressure. Provided the rise in cerebrovascular intraluminal pressure is sufficiently prominent, transient opening of the morphologic blood-brain barrier will occur. In the present study pressure increase, not sufficient in itself to cause barrier opening, was induced. However, at concomitant dilatation of the vessels – as induced by CO2 or papaverine – under otherwise identical pressure conditions a barrier opening was obtained. Hence, vasodilatation of cerebral vessels will increase their vulnerability to hypertension.
Influence of Locally Altered in vivo Shear Stress on Aortic Histamine-Forming Capacity and Aortic Albumin Uptake
Authors: Markle Ronald A. , Hollis Theodore M.
Published: September 2008

Effects of locally elevated shear stresses on thoracic aortic histamine formation and transmural albumin uptake have been examined under in vivo conditions in anesthetized male, mongrel dogs. Results indicate that if endothelium remains intact, significant linear relationships exist between the shear intensity and aortic histamine-forming capacity and aortic content of fluorescein-labeled bovine serum albumin following 20 h of circulation time. These data suggest that in vivo the aortic (and endothelial) histidine decarboxylase system is sensitive to local alterations in applied shear stress, and that de novo aortic histamine synthesis is involved in mediating shear-induced increases in aortic transmural permeability.
Contractility and the Length-Tension Relation of the Dog Anterior Tibial Artery
Authors: Price Joel M. , Davis D.L.
Published: September 2008

Active force (S) and rate of change of force (S) throughout the time of isometric contraction in electrically stimulated, circumferentially cut segments of dog anterior tibial artery were analyzed for dynamic indices of the contractile state. Previous works have determined indices that change with temperature but not with length (L) or calcium (Ca) and were designated indices of crossbridge dynamics. They assumed that changes in L and Ca change only the number of crossbridges between contractile filaments and temperature affects only the dynamics of individual crossbridges. We have shown: (1) specific ratios of S/S to be independent of L; (2) S/S at the same instant of time (V*CE) is related to an index from previous work which was defined as a velocity of internal shortening; (3) specific indices of S/S were decreased with lower temperature but increased with time in a Ca-free solution. Our results for a Ca-free solution do not agree with previous work but can be explained by changes of the smooth muscle cell membrane. This suggests that L-independent indices are useful for characterizing changes in the overall dynamic state of the tissue but are not necessarily representative of a change in crossbridge dynamics.
Neuroeffector Function of Isolated Portal Vein from Spontaneously Hypertensive and Wistar-Kyoto Rats: Dependence on External Calcium Concentration
Authors: Pegram Barbara L. , Ljung Bengt
Published: September 2008

The calcium dependence of the vascular neuroeffector function has been studied in the portal vein of spontaneously hypertensive Okamoto rats (SHR) and Wistar-Kyoto rats (WKY). The noradrenaline (NA) sensitivity of veins of both species, expressed in terms of ED50, was decreased to the same extent in relation to the reduction in Ca2+ ion concentration below 2.5 mM. The responses to individual NA concentrations at subnormal Ca2+ concentrations were better maintained, however, in portal veins from SHR than from WKY, indicating that the excitation contraction coupling mechanism is less dependent on external Ca2+ concentrations in the portal vein from SHR than from WKY. In both strains of rats the spontaneous myogenic activity of the vessel was depressed in low Ca2+ concentrations to a greater extent than responses to nerve stimulation, which, in turn, were more reduced than the excitatory responses to exogenous NA or acetylcholine (ACh). Transmitter release (fractional overflow of 3H-NA/impulse) was less dependent on Ca2+ concentrations than the contractile nerve stimulation response. The persistance of all responses in reduced Ca2+ concentrations was significantly greater in the portal vein of SHR. It is concluded that the phasic, spontaneously active smooth muscle of the rat portal vein is highly dependent on the external calcium concentration and that various induced responses persist to a varying degree in reduced Ca2+ concentrations. It is suggested that this is due to interference with electromechanical coupling as well as myogenic spread of activation. Induced responses of the portal vein from SHR are, in general, less affected by decreased Ca2+ concentrations than the WKY portal vein, indicating an altered vascular smooth muscle excitation-contraction coupling mechanism in spontaneous hypertension. Possibly an increased efficiency of the coupling mechanism may contribute to augment vascular responses in the development of hypertension and promote structural vascular changes.
Uptake and Metabolism of Noradrenaline by Blood Vessels of Perinephritic Hypertensive Dogs
Authors: Garrett J. , Castro-Tavares J. , Branco D.
Published: September 2008

Tissue noradrenaline content as well as uptake and metabolism of tritiated exogenous noradrenaline were studied comparatively, in vitro in mesenteric arteries, and in saphenous veins of normotensive and perinephritic hypertensive dogs. The influence of cocaine, iproniazid and 3’-4’-dihydroxy-2-methyµ-propiophenone (U-0521) on these variables wasalso investigated. The concentration of (–)-7-3H-noradrenaline used was 1.084 µM. No changes were observed in noradrenaline content, uptake and metabolism in saphenous vein strips obtained from normotensive or hypertensive animals. However, in mesenteric artery strips obtained from hypertensive dogs, a marked reduction in endogenous noradrenaline content was observed as well as a reduction in noradrenaline accumulation (20 weeks after surgery). The deamination pattern was also modified in these strips: the formation of DOPEGwas markedly diminished and the formation of DOMA was increased. These results agree well with the degeneration of the sympathetic innervation of the mesenteric arteries of hypertensive dogs described by Azevedo et al. (1981).
Ultrastructural Changes in Blood Vessels of Perinephritic Hypertensive Dogs
Authors: Azevedo Isabel , Castro-Tavares J. , Garrett J.
Published: September 2008

Mesenteric arteries and saphenous veins of control and perinephritic hypertensive dogs were studied with light and electron microscopy. 2 weeks after surgery there are ultrastructural changes, both in arteries and veins which are thought to be of hydroelectrolytic origin. These alterations are more marked 7 weeks after surgery and disappear thereafter. There are signs of increased protein synthesis activity in the smooth muscle of the mesenteric arteries, but not of the saphenous veins obtained 7 and 14 weeks after surgery, leading to a progressive hypertrophy of the muscular cells. The connective tissue augmented proportionally. Degeneration of adrenergic nerves in the arteries, accompanied by a parallel decrease in their noradrenaline content, constituted an unexpected finding clearly deserving further study.
Angiotensin I Conversion by the Microcirculation of the Nonhuman Primate
Authors: Cornish Kurtis G. , Gilmore Joseph P.
Published: September 2008

Previous studies have shown that angiotensin I (AI) is converted to angiotensin II (All) by converting enzyme (CE) or by tonin. Since all work on tonin has been done in the rodent, its relevance to the primate is yet to be shown. This study examines the conversion of AI to All by the cheek pouch microcirculation of the monkey (macaca fascicularis). In 9 of the 11 monkeys studied, the conversion of AI to Allwas blocked by converting enzyme inhibitor (CEI). However, in 2 older monkeys, AI conversion was not altered by CEI although the vascular response to AI was attenuated by both the All antagonist (saralasin) and the antibody to AII (Ab-AII). In these 2 older animals, renin substrate caused vasoconstriction that was not altered by CEI, but was reduced by saralasin and Ab-AII. It is concluded that the tonin-angiotensin system is not active in the young macaque, but may be present in the older animals.
Effects of Reserpinization, Surgical Denervation and in vitro Chemical Denervation with 6-Hydroxydopamine on the Contractile Response of Isolated Rabbit Ear Artery to Propranolol
Authors: Purdy Ralph E. , Ashbrook Donald W. , Hurlbut Diana E. , Reidy John P. , Stratford Robert E. , Watanabe Mitchell Y.
Published: September 2008

The contractile effect of propranolol in isolated rabbit ear artery was assessed in reserpinized and in surgically and chemically denervated blood vessels. Reserpinization and surgical denervation either had no effect on or enhanced the ear artery contractile response to 10–6 to 10-4M propranolol. In contrast, the contractile response to propranolol was nearly abolished after denervation of the ear artery in vitro with 6-hydroxydopamine (6-OHDA). Dose-response curves to norepinephrine were shifted to the left by factors of 4.9 in 6-OHDA denervated ear arteries and 15.6 in untreated arteries in the presence of 10–7M desipramine. The diluent for 6-OHDA shifted both the norepinephrine and propranolol dose-response curves to the right. It is proposed that propranolol caused a contractile response in ear artery by an action on the postsynaptic tissues of this vessel. 6-OHDA denervation caused nonspecific desensitization in rabbit ear artery leading to the loss of response of this vessel to propranolol.
Nonlinear Stress Field in Blood Vessels Under the Action of Connective Tissues
Authors: Misra J.C. , Roychoudhury K.
Published: September 2008

Finite deformations and stresses in vascular walls are studied analytically in the paper. Nonlinear viscoelastic constitutive relations suitably modified for the consideration of the anisotropic behavior of the vessel walls are used in the analysis. The time dependence of the inner surface and the force exerted by the surrounding connective tissues are also taken into account. Using approximations for short time ranges, a quantitative analysis is made in order to illustrate the applicability of the analytical study.
Regional Differences in the Density of Perivascular Nerves and Varicosities, Noradrenaline Content and Responses to Nerve Stimulation in the Rabbit Ear Artery
Authors: Griffith S.G. , Crowe R. , Lincoln J. , Haven A.J. , Burnstock G.
Published: September 2008

Quantitative image analysis of fluorescent nerves following histochemical localization of monoamines in stretch preparations of the rabbit ear artery (REA) reveals marked differences in the density of innervation between the proximal and distal regions. The innervation in the proximal region is about twice as dense as that in the distal region and there are approximately 10,500 and 6,500 varicosities per mm2 vessel area in these two regions, respectively. These varicosities have approximately the same mean diameter throughout the length of the vessel. The noradrenaline contents per gram wet weight of tissue in the proximal and distal regions are 1.93 and 0.94 µg, respectively. It is estimated that noradrenaline contents per mm2 nerve plexus area are 0.30 and 0.08 ng and that the nerve endings contain 2.8 × 10–14 and 1.2 × 10–14 g per varicosity in the proximal and distal REA, respectively. Sympathetic nerve stimulation in vitro with frequencies up to 8 Hz elicits larger and faster contractions in the proximal REA and the threshold frequency is less than in the distal region. This study also indicates that care should be taken to use the same region when using the REA for pharmacological and physiological studies.
Angiotensin II-Induced Relaxation of Vascular Smooth Muscle
Authors: Webb Clinton
Published: September 2008

The effects of angiotensin II (All) on contractile tension were studied in vascular smooth muscle from dogs, pigs and rabbits. Helically cut strips of renal veins were mounted in organ chambers and isometric contractions were recorded. Contraction of the venous strips was induced by application of 10–8 g/ml norepinephrine (NE). Subsequent addition of 5 × 10-8 g/ml All caused a triphasic response: (1) there was an initial contraction (subsequent contractions were tachyphylactic in all species); (2) the contraction was followed by a relaxation below the contraction induced by NE (subsequent relaxation responses were tachyphylactic in dog and pig veins), and (3) there was a return from the relaxation to the level of the NE-induced contraction. The duration of the entire response was approximately 5 min. The magnitude of the relaxation varied inversely with the level of the NE contraction when the contractile state was altered by changing the NE concentration. Conditions which inhibit the sodium pump (potassium-free solution and ouabain) and beta-adrenergic blockade with pro-pranolol had no effect on the All-induced relaxation. The relaxation was temperature sensitive. Inhibitors of prostaglandin synthesis (indomethacin and aspirin) and saralasin attenuated the relaxation in response to AIL Prostaglandins E1 and E2 and arachidonic acid caused relaxation of renal vein strips contracted with NE; the relaxant effect of arachidonic acid was blocked by indomethacin. These results suggest that: (1) All stimulates the synthesis of prostaglandins in isolated venous smooth muscle, and (2) endogenous prostaglandins modulate the response of venous smooth muscle to AIL
Potassium Depolarization of Adrenergic Varicosities in Resistance Arteries from SHR and WKY Rats
Authors: Whall, Jr. Clifford W. , Havlik Robert J. , Halpern William , Bohr David F.
Published: September 2008

We characterized the function of adrenergic nerve varicosities in mesenteric resistance arteries from spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats by observing contractile responses to depolarization with a high potassium solution (HiK). Intact rings of resistance arteries were mounted in a specialized muscle chamber for measurement of circumferential contractile forces. Contractile responses to exogenous norepinephrine (NE), to HiK, and to the combination of NE plus HiK were significantly greater in SHR compared to WKY vessels. Using either phentolamine or 6-hydroxydopamine-treated vessels to eliminate a neurogenic adrenergic response, we determined that a part of the HiK-induced contraction was due to NE released from nerve varicosities (i.e., the adrenergic component). In order to compare these adrenergic components for possible nerve-related differences, they were first normalized to their maximum exogenous NE responses. This normalized adrenergic component of SHR vessels (52 and 58% for phentolamine and 6-hyroxydopamine treatment, respectively) was significantly greater than that of the WKY vessels (35 and 37%). This greater adrenergic component could reflect either a greater vascular smooth muscle sensitivity to NE in arteries from SHR or an increase in NE concentration, or both.
Enhancement and Prolongation of Vascular Smooth Muscle Contraction by Aldosterone
Authors: Purdy Ralph E. , Weber Michael A.
Published: September 2008

Isolated rings of rabbit thoracic aorta were mounted in tissue baths for the measurement of isometric tension development and desipramine was added to all baths to block neuronal uptake of catecholamines. When these vessels were contracted to a steady-state of 1.5–3.5 g with norepinephrine, the addition of 1, 10 and 100 µM aldosterone caused a further contraction of 0.09, 0.47 and 0.8 g, respectively. Vessels contracted with norepinephrine and exposed to aldosterone were also immersed in mineral oil to trap a finite amount of norepinephrine within the receptor compartment of the tissue and the rate of relaxation was measured. The time to relax 50% (t½) in the presence of 100 µM aldosterone was approximately 18 min, while that in the presence of either ethanol diluent or 10 µM aldosterone was 7 min. When maximally effective concentrations of aldosterone and deoxycorticosterone acetate were used, the increases in norepinephrine-induced contractions and relaxation t½ values caused by these agents were identical. Combining these agents did not produce additive effects. Aldosterone also increased contractions and t½ values in tissues contracted with epinephrine but not in those contracted with methoxamine or 5-hydroxytryptamine. These findings support the conclusion that aldosterone enhances and prolongs contraction by inhibiting the removal of catecholamines from the receptor compartment of vascular smooth muscle.