Calcium and Contraction in the Rabbit Anterior Mesenteric–Portal Vein

1972 ◽  
Vol 50 (4) ◽  
pp. 289-299 ◽  
Author(s):  
G. A. Collins ◽  
M. C. Sutter ◽  
J. C. Teiser
Keyword(s):  
Portal Vein ◽  
Membrane Permeability ◽  
Time Course ◽  
Contractile Response ◽  
Calcium Influx ◽  
Contractile Activity ◽  
Krebs Solution ◽  
Free Solution ◽  
Membrane Bound ◽  
External Calcium

Studies were done measuring contractile activity in the isolated rabbit anterior mesenteric–portal vein (A.M.V.). The rabbit A.M.V. requires external calcium for both spontaneous activity and the initiation and maintenance of contractions to agonists.After bathing the tissues in calcium-free Krebs' solution containing 1 mM ethyleneglycoltetraacetic acid (EGTA) for 10 min, and then washing out the EGTA, the re-addition of calcium produced a contraction. The pre-addition of a small amount of calcium (0.1 mM) after EGTA treatment (while not inducing a contractile response) alters subsequent contractile responses to larger concentrations of calcium. This is interpreted as the ability of membrane-bound calcium to control membrane permeability to calcium.Other experiments involved bathing the tissues in calcium-free solution until no response was obtained to agonists, and then re-adding calcium. The time course of the responses to noradrenaline after calcium re-addition depended on the length of calcium incubation. This suggests that noradrenaline can release a loosely bound calcium fraction which may be involved in controlling calcium influx. This bound calcium, however, does not provide a major source of activator calcium in normal Krebs' solution.

scholarly journals Participation of NO in the vasodilatory action of isoespintanol

Revista Vitae ◽  
2019 ◽  
Vol 26 (2) ◽  
pp. 78-83
Author(s):  
Gustavo J. RINALDI ◽  
Benjamín ROJANO ◽  
Guillermo SCHINELLA ◽  
Susana M. MOSCA
Keyword(s):  
Nitric Oxide ◽  
Wistar Rats ◽  
Contractile Response ◽  
Calcium Influx ◽  
Free Solution ◽  
Vascular Effects ◽  
Vasodilator Effect ◽  
Vasodilatory Action ◽  
Vasodilator Action ◽  
Oxide Synthase

Background: accumulating evidence suggests that natural compounds and specifically monoterpenes exert a vasodilator action. Objetive: to investigate the vascular effects of isoespintanol (2-isopropil-3,6- dimetoxi-5-metilfenol, ISO) monoterpene isolated from the leaves of Oxandra cf xylopioides. Methods: thoracic aortic rings isolated from Wistar rats were contracted with KCl 80 mM and then relaxed by exposure to Ca2+-free solution in absence and in presence of ISO 0.6 mg/mL. The force/tissue ratio (F/W) and the time to obtain 50% of relaxation (T-50) were used to assess the maximal contractile response and the relaxation, respectively. To examine the participation of NO additional experiments were performed under inhibition of nitric oxide synthase with L-NAME (L-NG-Nitroarginine methyl ester). Results: ISO significantly decreased the F/W ratio (257 ± 19 vs. 360 ± 18) and did not change T-50. In presence of L-NAME the effects of ISO on contractile response was abolished. Conclusions: these results demonstrate that ISO exerts a vasodilator effect through NO- dependent pathways and suggest that an inhibition of calcium influx could be the involved mechanism.

Rhythmic coronary arterial contractions: changes with time and membrane potential

1986 ◽  
Vol 250 (3) ◽  
pp. H524-H529 ◽  
Author(s):  
K. D. Keef ◽  
G. Ross
Keyword(s):  
Membrane Potential ◽  
Coronary Artery ◽  
Time Course ◽  
Sodium Pump ◽  
Contractile Response ◽  
Resting Membrane Potential ◽  
Krebs Solution ◽  
Contractile Responses ◽  
Rabbit Coronary Artery ◽  
Rhythmic Contractions

Responses of isolated rabbit coronary artery segments to KCl and 2-(2-aminoethyl)-pyridine (AEP) were studied. Vessels stored at 2 degrees C for 24 h developed spontaneous rhythmic contractions during the first 20 min in Krebs solution at 37 degrees C. The contractile response to KCl or AEP declined to a minimum at 60 min [i.e., time zero (to) +60], increased to a peak at to +150 and then again declined. Resting membrane potential (Em) was less than or equal to -40 mV at to +20, -70 mV at to +30-60 and -50 mV at to +240-360 min. Rhythmic contractile responses were frequent and were associated with changes in Em. Vessels that were not cold stored did not hyperpolarize, nor did they show the early decline in response. Vessels stored at 2 degrees C for 24 h and then tested at 22-23 degrees C exhibited a similar pattern of changes in contraction but the time course was more protracted. We conclude that contractile responses are initially modulated by changes in Em associated with an increase then decrease in the activity of the sodium pump. Later changes in reactivity are due to a different mechanism.

scholarly journals Effect of External Calcium and of Temperature on Contraction in Snake Muscle Fibers

1974 ◽  
Vol 63 (4) ◽  
pp. 415-431 ◽  
Author(s):  
Hiroshi Washio
Keyword(s):  
Time Course ◽  
Contractile Response ◽  
Muscle Fibers ◽  
Outward Current ◽  
Bathing Solution ◽  
Minimum Duration ◽  
Delayed Rectification ◽  
Rate Of Recovery ◽  
Lower Temperature ◽  
External Calcium

The effect of external calcium and of temperature on the contractile responses has been studied in voltage clamped snake twitch muscle fibers. Increasing [Ca++]o from 0.2 to 7.0 mM raised contractile threshold by 15–20 mV, the latter coinciding with the appearance of delayed rectification. The duration of contracture, the rates of rise and decay of tension depended on the level of depolarization and [Ca++]o. The minimum duration of repolarization necessary to restore the contractile response was much shorter in high [Ca++]o. When the bathing solution was cooled to 10 from 20°C the time-course of contracture was markedly prolonged and the outward current was reduced without significant change in maximum tension. The threshold for contraction tended to be somewhat lower at the lower temperature. The contractile repriming was much slower at low temperature. However, reduction in temperature slowed the rate of recovery much less at low [Ca++]o than at normal [Ca++]o.

scholarly journals Some Factors Affecting the Time Course of the Recovery of Contracture Ability Following a Potassium Contracture in Frog Striated Muscle

1965 ◽  
Vol 48 (6) ◽  
pp. 975-983 ◽  
Author(s):  
J. V. Milligan ◽  
C. Edwards
Keyword(s):  
Recovery Rate ◽  
Time Course ◽  
Calcium Concentration ◽  
Striated Muscle ◽  
Free Solution ◽  
Chemical Binding ◽  
Factors Affecting ◽  
Temperature Changes ◽  
Potassium Contracture ◽  
External Calcium

The recovery rate of contracture ability after a K contracture was shown to be initially dependent upon the rate of repolarization and later to be dependent upon a process which was sensitive to concentration and temperature changes in a manner consistent with chemical binding. It was shown qualitatively that repolarization did not depend on the presence of external calcium and the second process was studied by allowing the muscle to repolarize for 2 minutes in calcium-free solution following a K contracture. Recovery after this procedure was speeded by decreasing either the concentration of potassium in the contracture solution or its temperature and was slowed by either decreasing the calcium concentration of the recovery solution or its temperature or by increasing the duration of the exposure to potassium.

Endothelin receptors and activity differ in human, dog, and rabbit lung

1996 ◽  
Vol 270 (1) ◽  
pp. L37-L43 ◽  
Author(s):  
K. O. McKay ◽  
C. L. Armour ◽  
J. L. Black
Keyword(s):  
Time Course ◽  
Contractile Response ◽  
Calcium Influx ◽  
Extracellular Calcium ◽  
Rabbit Lung ◽  
Potential Models ◽  
Kinase C ◽  
Voltage Dependent ◽  
Human Airways ◽  
Pkc Activation

In this study, we have examined dog and rabbit airways as potential models for human airways in regard to the activity of endothelin. The receptors involved in the response to endothelin-1 (ET-1) in airway tissue from human, rabbit, and dog lung were investigated, as was the mechanism responsible for the contraction to ET-1 in tissue from the three species. By using specific endothelin receptor agonists and antagonists, we have demonstrated that ETB receptors predominate in rabbit and human airways and ETA receptors in dog airways. The contraction to ET-1 is not dependent on cyclooxygenase products of arachidonic acid, as indomethacin had no effect on the response to ET-1. Extracellular calcium influx via voltage-dependent channels is necessary for contraction to ET-1 in rabbit and dog airways. These results are in contrast to our previously reported results in human airways, in which neither removal of extracellular calcium nor verapamil affected the ET-1 response. The sustained phase of the contraction to ET-1 in all three species may be mediated in part by activation of protein kinase C (PKC), as the inhibitor staurosporine significantly altered the time course of the response to endothelin. We therefore conclude that in rabbit airways ET-1 activates ETB receptors, triggers the influx of extracellular calcium through voltage-dependent channels, and induces a contractile response that is, in part, dependent upon stimulation of PKC. The same mechanism is triggered in dog bronchus; however, the receptors involved in this species are of the ETA type. Finally, in human airways, the contractile response to ET-1, while independent of extracellular calcium influx, is dependent upon PKC activation after binding of the peptide to ETB receptors.

In vitro effects of desoxycorticosterone on vascular smooth muscle

1979 ◽  
Vol 237 (2) ◽  
pp. H197-H203
Author(s):  
M. F. Koehler ◽  
R. C. Webb ◽  
A. W. Jones ◽  
D. F. Bohr
Keyword(s):  
Membrane Permeability ◽  
Calcium Binding ◽  
Contractile Response ◽  
Indirect Evidence ◽  
Rabbit Aorta ◽  
Rat Aorta ◽  
Free Solution ◽  
Tetraacetic Acid ◽  
In Vitro Effects

We present evidence in accord with the observations of S. Kalsner (Br. J. Pharmacol. 36: 582-593, 1969) that in the rabbit aorta, desoxycorticosterone (DOC) potentiates the contractile response to certain catecholamines by inhibiting their degradation by catechol-O-methyltransferase. In contrast, DOC depresses the contractile responses in rat aorta and tail arteries. To elucidate the mechanism of this depression the effect of DOC was evaluated under various conditions. DOC depressed the contractile response to epinephrine, phenylephrine, KCl, and angiotensin II. The depression was unaltered by ouabain or by a potassium-free solution, indicating that DOC did not produce its depression by altering Na-K-ATPase activity. The depression is unaltered in a chloride-free solution, demonstrating that the DOC effect is not caused by a change in membrane permeability to chloride. Radioisotope studies demonstrate that DOC does not alter membrane permeability to potassium. Removal of extracellular calcium with EGTA (ethylene glycol-bis (beta-aminoethyl ether) N, N'-tetraacetic acid) significantly reduced the magnitude of the DOC depression. Indirect evidence is presented suggesting that DOC might increase calcium binding to the plasma membrane, resulting in its stabilization and hence in a depression of the contractile response.

Quantitative Aspects of Cyclic AMP and Relaxation in the Rabbit Anterior Mesenteric-Portal Vein

1975 ◽  
Vol 53 (6) ◽  
pp. 989-997 ◽  
Author(s):  
G. A. Collins ◽  
M. C. Sutter
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Portal Vein ◽  
Muscle Relaxation ◽  
Phosphodiesterase Inhibitors ◽  
Smooth Muscle Relaxation ◽  
Krebs Solution ◽  
Free Solution ◽  
Dibutyryl Cyclic Amp ◽  
Extracellular Sodium

Rabbit anterior mesenteric-portal vein was shown to exhibit a positive correlation between relaxation and cyclic AMP levels using different concentrations of isoproterenol for varying exposure times. No consistent relationship was found between cyclic AMP and relaxation using a series of phosphodiesterase inhibitors (papaverine, SC2964, or RA233). In sodium-free (Tris-substituted) Krebs' solution, the addition of isoproterenol still increased, cyclic AMP levels, but there was no relaxation. Dibutyryl cyclic AMP was also ineffective in sodium-free solution. Under identical conditions, both relaxation and increases in cyclic AMP produced by papaverine and SC2964 were found to be independent of extracellular sodium. We conclude, therefore, that increased cyclic AMP may be involved in isoproterenol-induced relaxation possibly acting via increased Na+–Ca2+ exchange, but plays only a small role, if any, in smooth muscle relaxation produced by papaverine, RA233, or SC2964.

The Effects of Manganese on the Rabbit Anterior Mesenteric–Portal Vein

1972 ◽  
Vol 50 (4) ◽  
pp. 300-309 ◽  
Author(s):  
G. A. Collins ◽  
M. C. Sutter ◽  
J. C. Teiser
Keyword(s):  
Portal Vein ◽  
Calcium Concentration ◽  
Calcium Influx ◽  
Extracellular Fluid ◽  
Inhibitory Effects ◽  
Competitive Kinetics ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials ◽  
Tonic Phase ◽  
External Calcium

The effects of manganese and lanthanum were tested on the contractile responses of the rabbit anterior mesenteric–portal vein (A.M.V.). Since these ions have been shown to block calcium fluxes in other tissues, examining their effects may give information concerning the importance of calcium influx for contractions of the A.M.V. The effects of the two cations on the A.M.V. were found to be similar except that lanthanum was more potent and its inhibitory effects were not readily reversible. Spontaneous action potentials and their associated contractions were abolished by the addition of 0.5 mM Mn2+. This inhibition could be rapidly reversed by adding EDTA to chelate the manganese. Manganese inhibited the responses to all agonists tested (noradrenaline, histamine, serotonin, procaine, and KCl). The inhibition of responses to all agonists but procaine could be partially reversed by raising the external calcium concentration. The interaction between calcium and manganese follows competitive kinetics. Adding manganese during the tonic phase of a contraction evoked by 10−6 g/ml noradrenaline resulted in a relaxation to a decreased, but sustained, tension. The inhibitory effects of manganese add further evidence that an influx of calcium from the extracellular fluid is required for spontaneous activity and for both the initiation and maintenance of contractions to agonists in the rabbit A.M.V.

Effect of plasma from hypertensive patients on contractile response of vascular smooth muscle from normotensive rat

1989 ◽  
Vol 67 (10) ◽  
pp. 1272-1277 ◽  
Author(s):  
G. Pillai ◽  
M. C. Sutter
Keyword(s):  
Smooth Muscle ◽  
Portal Vein ◽  
Vascular Smooth Muscle ◽  
Spontaneous Activity ◽  
Mechanical Response ◽  
Contractile Response ◽  
Contractile Activity ◽  
Plasma Samples ◽  
Hypertensive Patients ◽  
Plasma Factor

This study examines whether incubation with plasma from essential hypertensive patients increases the contractile activity of vascular smooth muscle from rats in response to noradrenaline (NA) and potassium (K+). Plasma samples were obtained from age- and sex-matched essential hypertensive patients and normotensive people. Vascular strips were prepared from aorta and portal veins of normotensive rats and placed in physiological solution in muscle baths for measurement of mechanical response. Aortic strips exposed to hypertensive plasma showed increased responsiveness to NA compared with normotensive plasma, but K+ caused an opposite effect. Portal vein exposed to normotensive or hypertensive plasma did not produce any response to NA, but the responsiveness produced in the presence of normotensive plasma to K+ was higher than that of hypertensive plasma. Portal vein exposed to normotensive plasma or hypertensive plasma showed a dose-dependent increase in the spontaneous activity up to 50% concentration of the plasma samples, but further increase in the concentration of plasma inhibited the spontaneous activity. Spontaneous activity at any given concentration of hypertensive plasma was significantly higher than that of normotensive plasma. The spontaneous activity in the presence of heated or unheated normotensive plasma or unheated normotensive serum was not significantly different from each other. These results indicate that the plasma factor from hypertensive patients, which alters the reactivity of vascular smooth muscle from normotensive rat, is present in the serum fraction and is not heat sensitive.Key words: hypertension, plasma, contractile response, circulating factor, spontaneous activity.

Chronic treatment of rats with D-600 causes a compensatory decrease in the calcium requirement for contractility of vascular smooth and cardiac muscles

1985 ◽  
Vol 63 (5) ◽  
pp. 495-499
Author(s):  
Catherine C. Y. Pang ◽  
Morley C. Sutter
Keyword(s):  
Portal Vein ◽  
Wistar Rats ◽  
Chronic Treatment ◽  
Contractile Response ◽  
Contractile Activity ◽  
Intraventricular Pressure ◽  
Calcium Requirement ◽  
Cardiac Muscles ◽  
Perfused Hearts

We studied the effects of chronic hypotensive treatment of normotensive Wistar rats (NWR) with methoxyverapamil (D-600) and hydralazine on in vitro contractile response of aortic strips, portal vein strips, and Langendorff-perfused hearts in normal (2.5 mM) and low (0.2 mM) calcium (Ca). Portal vein strips from rats treated with D-600, compared with the same strips from control and hydralazine-treated rats, developed greater spontaneous contractile activity in normal Ca and retained greater responses to norepinephrine (NE) and 80 mM K in low Ca. Aortic strips from all three groups of rats retained similar responses to NE and K in low Ca. Hearts from D-600-treated rats produced less intraventricular pressure (IVP) to isoproterenol (ISO) than hearts from control and hydralazine-treated rats in normal Ca but greater IVP to ISO than hearts from the other two groups of rats in low Ca. Thus, chronic treatment of NWR with D-600 but not with hydralazine resulted in the reduction of Ca requirement for contractile activities of the portal vein and the myocardium.

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