Phosphagen and metabolite content during contraction in porcine carotid artery

1983 ◽  
Vol 244 (5) ◽  
pp. C385-C390 ◽  
Author(s):  
J. M. Krisanda ◽  
R. J. Paul
Keyword(s):  
Steady State ◽  
Carotid Artery ◽  
Isometric Contraction ◽  
Time Course ◽  
Isometric Force ◽  
Apparent Lack ◽  
Tissue Extracts ◽  
Metabolic Signal ◽  
Metabolite Content ◽  
Porcine Carotid Artery

Previous studies (Paul, R. J. Chemical energetics of vascular smooth muscle. In: Handbook of Physiology: The Cardiovascular System. Bethesda, MD: Am. Physiol. Soc., 1980, p. 201-235) have shown that vascular oxygen consumption reaches a steady state at approximately twice the basal rate during maintenance of isometric contraction. The time course of the attainment of a metabolic steady state, the metabolic signal for the observed increase in respiration, and the contribution of endogenous phosphagens to the energetics of isometric contraction are not known with certainty. To this end, the time course of the tissue content of ATP, ADP, AMP, phosphocreatine (PCr), inorganic phosphate (Pi), and lactate were measured during a KCl-induced isometric contraction in porcine carotid artery and compared with values in the basal state. Oxygenated unpoisoned strips were frozen at 0, 0.5, 1, and 15 min of contraction, and tissue extracts were analyzed using analytical isotachophoresis. No statistically significant changes from the basal levels of ATP and PCr were measured. A small but significant increase in ADP was seen at all times. An increase in Pi of 1.25 mumol/g was observed at 0.5 min, which decreased in time. Tissue lactate content increased by 1.79 mumol/g after 1 min of contraction. The calculated range of cellular free ADP (ADPfree), 44-123 microM, may be sufficient to saturate oxidative phosphorylation. This and the apparent lack of change of ADPfree from basal during contraction suggest that it does not play a role in the coordination of metabolism and contractility. From as early as 0.5 min, when less than 40% of peak isometric force is attained, intermediary metabolism provides the total ATP required for contraction.

Energetics of isometric contraction in porcine carotid artery

1984 ◽  
Vol 246 (5) ◽  
pp. C510-C519 ◽  
Author(s):  
J. M. Krisanda ◽  
R. J. Paul
Keyword(s):  
Steady State ◽  
Carotid Artery ◽  
Time Course ◽  
Shortening Velocity ◽  
Tension Development ◽  
Electrode Response ◽  
Length Step ◽  
Steady State Levels ◽  
O2 Diffusion ◽  
Porcine Carotid Artery

The rate of ATP utilization ( JATP ) and unloaded shortening velocity ( Vus ) of porcine carotid artery were studied during tension development and maintenance to assess the importance of mechanisms proposed to account for its high economy of tension maintenance. Previous work from our laboratory established that the rate of O2 consumption ( JO2 ) can be used to measure rates of tissue phosphagen utilization as early as 30 s after initiation of contraction. Studies at 37 degrees C of tissue JO2 indicated the following. 1) The basal JO2 was 0.069 +/- 0.017 mumol O2 X min-1 X g-1) (n = 10). During steady-state tension maintenance suprabasal JO2 was 0.079 +/- 0.012 mumol O2 X min-1 X g-1 for tissues stimulated with KCl (n = 11) and 0.213 +/- 0.022 (n = 3) for tissues stimulated with KCl + histamine. 2) For both stimulation conditions an initial elevated (peak) suprabasal JO2 was observed that correlated with the rate of tension development. The peak suprabasal JO2 was approximately twice the steady-state suprabasal JO2 measured 10 min after stimulation. 3) There was no significant change in JO2 during tension redevelopment after a rapid length step at 15–20 min after stimulation (n = 4). Studies of Vus indicated the following. 1) During steady-state tension maintenance Vus was 0.008 +/- 0.001 tissue lengths/s for tissues stimulated with KCl (n = 13) tissue lengths/s for tissues stimulated with KCl + histamine (n = 6). 2) An initial twofold peak in Vus was observed at 0.25–0.5 min in that decreased to steady-state levels by 4 min after KCl stimulation, whereas minor decreases in Vus still occurred until 10–20 min after KCl + histamine stimulation. 3) The measured transient in Vus , although biphasic, does not temporally correlate with the transient in JO2 even after the JO2 time course was corrected for delays resulting from O2 diffusion and the electrode response time. The mechanism underlying the observed maximum change of two- to fourfold in both JATP and Vus is not sufficient to account for the high economy of tension maintenance.

Dependence of force, velocity, and O2 consumption on [Ca2+]o in porcine carotid artery

1988 ◽  
Vol 255 (3) ◽  
pp. C393-C400 ◽  
Author(s):  
J. M. Krisanda ◽  
R. J. Paul
Keyword(s):  
Steady State ◽  
Carotid Artery ◽  
Isometric Force ◽  
Test Method ◽  
O2 Consumption ◽  
Shortening Velocity ◽  
Tension Development ◽  
Calcium Dependent ◽  
The Difference ◽  
Porcine Carotid Artery

The relationship between extracellular calcium concentration ([Ca2+]o), isometric force (Fo), unloaded shortening velocity (Vus), and the rate of ATP utilization (JATP) were studied in vascular smooth muscle (VSM) during the steady state of an isometric contraction at 37 degrees C. Experiments were conducted on porcine carotid artery media strip and ring preparations that were stimulated with 109 mM KCl substituted for NaCl. Unloaded shortening velocity was estimated by the "slack" test method. Both Fo and Vus were dependent on [Ca2+]o. Vus at 7.5 mM [Ca2+]o was 1.7 times greater than Vus at 1.6 mM [Ca2+]o. The difference in force at these two Ca2+ concentrations was more variable than Vus, but in general was less than the change in Vus. The rate of ATP utilization was assessed from steady-state measurements of tissue O2 consumption. Increasing [Ca2+]o in the range of 0.15-7.5 mM resulted in an increase in both JATP and Fo. The relation between JATP and Fo was nonlinear with JATP increasing proportionately more than Fo between 1.6 and 7.5 mM Ca2+. The calcium-dependent increase in JATP appears to be primarily related to contractile protein interaction, since the effect of [Ca2+]o on JATP was substantially reduced during stimulation at short muscle lengths (Lmin), where tension development is absent. The economy of tension maintenance was 3.3. times greater when measured in the [Ca2+]o range of 0.15 and 1.6 mM than when measured at 1.6 to 7.5 mM [Ca2+]o. These data indicate that [Ca2+]o may regulate both the number and the rate of cycling of cross bridges in porcine carotid artery.

scholarly journals The influence of residual force enhancement on spinal and supraspinal excitability

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5421 ◽  
Author(s):  
Caleb T. Sypkes ◽  
Benjamin J. Kozlowski ◽  
Jordan Grant ◽  
Leah R. Bent ◽  
Chris J. McNeil ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Evoked Potentials ◽  
Isometric Contraction ◽  
Motor Evoked Potentials ◽  
Isometric Force ◽  
Force Enhancement ◽  
Active Muscle ◽  
Residual Force ◽  
Residual Force Enhancement

Background Following active muscle lengthening, there is an increase in steady-state isometric force as compared with a purely isometric contraction at the same muscle length and level of activation. This fundamental property of skeletal muscle is known as residual force enhancement (RFE). While the basic mechanisms contributing to this increase in steady-state isometric force have been well documented, changes in central nervous system (CNS) excitability for submaximal contractions during RFE are unclear. The purpose of this study was to investigate spinal and supraspinal excitability in the RFE isometric steady-state following active lengthening of the ankle dorsiflexor muscles. Methods A total of 11 male participants (20–28 years) performed dorsiflexions at a constant level of electromyographic activity (40% of maximum). Half of the contractions were purely isometric (8 s at an ankle angle of 130°), and the other half were during the RFE isometric steady-state following active lengthening (2 s isometric at 90°, a 1 s lengthening phase at 40°/s, and 5 s at 130°). Motor evoked potentials (MEPs), cervicomedullary motor evoked potentials (CMEPs), and compound muscle action potentials (M-waves) were recorded from the tibialis anterior during the purely isometric contraction and RFE isometric steady-state. Results Compared to the purely isometric condition, following active lengthening, there was 10% RFE (p < 0.05), with a 17% decrease in normalized CMEP amplitude (CMEP/Mmax) (p < 0.05) and no change in normalized MEP amplitude (MEP/CMEP) (p > 0.05). Discussion These results indicate that spinal excitability is reduced during submaximal voluntary contractions in the RFE state with no change in supraspinal excitability. These findings may have further implications to everyday life offering insight into how the CNS optimizes control of skeletal muscle following submaximal active muscle lengthening.

Smooth muscle energetics and theories of cross-bridge regulation

1990 ◽  
Vol 258 (2) ◽  
pp. C369-C375 ◽  
Author(s):  
R. J. Paul
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Steady State ◽  
Time Course ◽  
Isometric Force ◽  
Muscle Energetics ◽  
Cross Bridge ◽  
Tension Cost ◽  
Low Tension ◽  
Smooth Muscle Energetics

The energetics of smooth muscle is characterized by low tension cost (rate of ATP utilization per isometric force/cross-section area), ranging from 100- to 500-fold less than skeletal muscle. The efficiency (ATP usage per work) of smooth muscle, although less well documented, is also somewhat (4-fold) less than skeletal muscle. Another well-known characteristic of smooth muscle is the linear relation between the steady-state of ATP utilization (JATP) and isometric force. Recently, Murphy and colleagues [C.-M. Hai and R. A. Murphy. Am. J. Physiol. 254 (Cell Physiol. 23) C99-C106, 1988] have put forth a kinetic model of cross-bridge regulation that predicts the time course of stress and myosin light chain phosphorylation (MLC-Pi). The energetics consequences of this model, in brief, are that the low tension cost is partly attributed to a slow detachment rate of the myosin cross bridge when dephosphorylated when attached to actin ("latch state"), whereas the lower efficiency is ascribed to a high rate of myosin phosphorylation-dephosphorylation inherent to a fit of data to this kinetic scheme. This latter corollary is somewhat controversial in light of current interpretations of smooth muscle energetics data. Using SCoP software (National Biomedical Simulation Resource, Duke University), we tested this model in terms of fitting existing data with respect to 1) is a high myosin-dephosphorylation adenosine triphosphatase (ATPase) necessary to fit the available data on the time course of stress and MLC-Pi?; and 2) can this model predict the observed linear relation between the steady-state rate of ATP hydrolysis (JATP) and isometric force?(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Variations in cross-bridge attachment rate and tension with phosphorylation of myosin in mammalian skinned skeletal muscle fibers. Implications for twitch potentiation in intact muscle.

1989 ◽  
Vol 93 (5) ◽  
pp. 855-883 ◽  
Author(s):  
J M Metzger ◽  
M L Greaser ◽  
R L Moss
Keyword(s):  
Steady State ◽  
Light Chain ◽  
Time Course ◽  
Myosin Light Chain ◽  
Isometric Force ◽  
Vastus Lateralis ◽  
Isometric Tension ◽  
National Academy Of Sciences ◽  
Cross Bridge ◽  
Myosin Light Chain 2

The Ca2+ sensitivities of the rate constant of tension redevelopment (ktr; Brenner, B., and E. Eisenberg. 1986. Proceedings of the National Academy of Sciences. 83:3542-3546) and isometric force during steady-state activation were examined as functions of myosin light chain 2 (LC2) phosphorylation in skinned single fibers from rabbit and rat fast-twitch skeletal muscles. To measure ktr the fiber was activated with Ca2+ and steady isometric tension was allowed to develop; subsequently, the fiber was rapidly (less than 1 ms) released to a shorter length and then reextended by approximately 200 nm per half sarcomere. This maneuver resulted in the complete dissociation of cross-bridges from actin, so that the subsequent redevelopment of tension was related to the rate of cross-bridge reattachment. The time course of tension redevelopment, which was recorded under sarcomere length control, was best fit by a first-order exponential equation (i.e., tension = C(1 - e-kt) to obtain the value of ktr. In control fibers, ktr increased sigmoidally with increases in [Ca2+]; maximum values of ktr were obtained at pCa 4.5 and were significantly greater in rat superficial vastus lateralis fibers (26.1 +/- 1.2 s-1 at 15 degrees C) than in rabbit psoas fibers (18.7 +/- 1.0 s-1). Phosphorylation of LC2 was accomplished by repeated Ca2+ activations (pCa 4.5) of the fibers in solutions containing 6 microM calmodulin and 0.5 microM myosin light chain kinase, a protocol that resulted in an increase in LC2 phosphorylation from approximately 10% in the control fibers to greater than 80% after treatment. After phosphorylation, ktr was unchanged at maximum or very low levels of Ca2+ activation. However, at intermediate levels of Ca2+ activation, between pCa 5.5 and 6.2, there was a significant increase in ktr such that this portion of the ktr-pCa relationship was shifted to the left. The steady-state isometric tension-pCa relationship, which in control fibers was left shifted with respect to the ktr-pCa relationship, was further left-shifted after LC2 phosphorylation. Phosphorylation of LC2 had no effect upon steady-state tension during maximum Ca2+ activation. In fibers from which troponin C was partially extracted to disrupt molecular cooperativity within the thin filament (Moss et al. 1985. Journal of General Physiology. 86:585-600), the effect of LC2 phosphorylation to increase the Ca2+ sensitivity of steady-state isometric force was no longer evident, although the effect of phosphorylation to increase ktr was unaffected by this maneuver.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Magnesium Therapy for Subarachnoid Hemorrhage Induced Cerebral Vasospasm as Assessed by In Vitro Studies on the Porcine Carotid Artery

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 330-330
Author(s):  
Gail J Pyne ◽  
Shinsuke Nakayama ◽  
Ondrej J Choutka ◽  
Thomas Ad Cadoux-Hudson ◽  
Joseph F Clark
Keyword(s):  
Smooth Muscle ◽  
Oxygen Consumption ◽  
Subarachnoid Hemorrhage ◽  
Carotid Artery ◽  
Vascular Smooth Muscle ◽  
Cerebral Vasospasm ◽  
Isometric Force ◽  
Intracellular Magnesium ◽  
Porcine Carotid Artery

82 Background: Mg 2+ has been used therapeutically in the treatment of eclampsia and it has recently become a novel avenue in the treatment of stroke because it can relax vascular smooth muscle. Currently there is a clinical trial, on going in England, involving Mg 2+ administration to stroke patients. But relatively little is known regarding the function or mechanism of Mg2+ treatment following subarachnoid hemorrhage (SAH). We therefore set out to determine if Mg 2+ could be used to prevent or reverse the in vitro vasospasm caused by the CSF from vasospastic (SAH) patients. Methods: Oxygen consumption and isometric force measurements of the isolated porcine carotid artery were used to assess the functional and metabolic responses of the vascular smooth muscle following stimulation by CSF from SAH patients with cerebral vasospasm. We used a method of exposing the vascular smooth muscle to 12 mM MgCl 2 for 1 hour to increase intracellular magnesium. This method has been shown to increase intracellular Mg 2+ to levels reached with two to three days of Mg 2+ therapy. Results: CSF from SAH patients with vasospasm will cause vasospasm when applied to vessels in vitro . Following this in vitro vasospasm, Mg 2+ caused a dose dependant decrease in tension (relaxation) following exposure to CSF from vasospasm patients. Exposure of vessels to 12 mM Mg 2+ normalized the rate of relaxation in the presence of CSF from SAH patients was normalized (2.70±0.71 Nm -2 s -1 in the presence of CSF; 15.8±4.20 Nm -2 s -1 with CSF and Mg 2+ ; and 16.1±4.85 Nm -2 s -1 without CSF). Mg 2. significantly (P≤0.05) decreased the rate of oxygen consumption observed when stimulated by CSF (0.70±0.03 μmol O 2 min -1 g -1 with CSF alone and 0.46±0.08 μmol O 2 min -1 g 1 with CSF and Mg 2+ ). Conclusion: These results suggest that Mg 2+ is a potent vasodilator that helps to normalize contractile behavior and metabolism of the porcine carotid artery exposed to the CSF of SAH patients with vasospasm. Therefore, Mg 2+ therapy is a possible avenue for treating patients with cerebral vasospasm by causing a relaxation of vascular smooth muscle.

Inward rectification in rat nucleus accumbens neurons

1989 ◽  
Vol 62 (6) ◽  
pp. 1280-1286 ◽  
Author(s):  
N. Uchimura ◽  
E. Cherubini ◽  
R. A. North
Keyword(s):  
Steady State ◽  
Nucleus Accumbens ◽  
Time Course ◽  
Potassium Conductance ◽  
Resting Potential ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Potential Range ◽  
Inward Current ◽  
Rat Nucleus Accumbens

1. Intracellular recordings were made from neurons in slices cut from the rat nucleus accumbens septi. Membrane currents were measured with a single-electrode voltage-clamp amplifier in the potential range -50 to -140 mV. 2. In control conditions (2.5 mM potassium), the resting membrane potential of the neurons was -83.4 +/- 1.1 (SE) mV (n = 157). Steady state membrane conductance was voltage dependent, being 34.8 +/- 1.7 nS (n = 25) at -100 mV and 8.0 +/- 0.7 nS (n = 25) at -60 mV. 3. Barium (1 microM) markedly reduced the inward rectification and caused a small inward current (40.6 +/- 8.7 pA, n = 8) at the resting potential. These effects became larger with higher barium concentrations, and, in 100 microM barium, the current-voltage relation was straight. 4. The block of the inward current by barium (at -130 mV) occurred with an exponential time course; the time constant was approximately 1 s at 1 microM barium and less than 90 ms with 100 microM. Strontium had effects similar to those of barium, but 1000-fold higher concentrations were required. Cesium chloride (2 mM) and rubidium chloride (2 mM) also blocked the inward rectification; their action reached steady state within 50 ms. 5. It is concluded that the nucleus accumbens neurons have a potassium conductance with many features of a typical inward rectifier and that this contributes to the potassium conductance at the resting potential.

The calcium inhibitor SR33805 reduces intimal formation following injury of the porcine carotid artery

2001 ◽  
Vol 154 (2) ◽  
pp. 301-308 ◽  
Author(s):  
Patricia Hainaud ◽  
Michel Bonneau ◽  
Georges Pignaud ◽  
Claire Bal dit Sollier ◽  
Patrick André ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Porcine Carotid Artery
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