The temperature dependence of ionic influences on contractile function in frog twitch muscle

1980 ◽  
Vol 58 (1) ◽  
pp. 74-84 ◽  
Author(s):  
J. G. Foulks ◽  
Lillian Morishita
Keyword(s):  
Temperature Dependence ◽  
Skeletal Muscles ◽  
Time Course ◽  
Contractile Function ◽  
Divalent Cations ◽  
Organic Anion ◽  
Ionic Composition ◽  
Amino Groups ◽  
Chloride Solutions ◽  
Reduced Temperature

Alterations in the ionic composition of the medium produce striking changes in the potential-dependent contractile responses of skeletal muscles. This study was undertaken to examine the temperature dependence of some of these effects. The suppression of maximal K contractures of frog toe muscles in media lacking divalent cations was largely overcome by a sufficient increase in temperature. The restoration of K contractures by perchlorate in the absence of divalent cations was prevented by a sufficient decrease in temperature. The effect of perchlorate was to shift the temperature dependence of these contractures toward lower temperatures. The reduction in the amplitude of maximal K contractures in the absence of divalent cations was less marked after pretreatment with a reagent (trinitrobenzenesulfonate) that selectively modifies free amino groups, although the temperature dependence of these contractures was unchanged. The reduction in the amplitude of K contractures in the presence of an organic anion (hexanoate) was partially antagonized both by an increase in temperature or by a decrease in temperature, effects that resemble those observed in solutions in which the divalent cation concentration was reduced. In chloride solutions, the relation between [K]0 and K contractures was shifted toward lower [K]0 by an increase in temperature, whereas in perchlorate solutions increased temperature produced a shift in the opposite direction. The shift in this relation toward lower [K]0 at reduced temperature, and the accelerated time course of K contractures with an increase in temperature were similar in perchlorate and in chloride solutions. Thermodynamic analysis by Arrhenius plots indicated that the influence of divalent cations and perchlorate anions on K contractures may be the result of their effects on hydrational factors.

The influence of D2O, perchlorate, and variation in temperature on the potential-dependent contractile function of frog skeletal muscle

1985 ◽  
Vol 63 (6) ◽  
pp. 693-703
Author(s):  
James G. Foulks ◽  
Lillian Morishita
Keyword(s):  
Skeletal Muscle ◽  
Contractile Function ◽  
Divalent Cations ◽  
Conformational Transitions ◽  
The Other ◽  
Frog Skeletal Muscle ◽  
Solvent Structure ◽  
Opposing Effects ◽  
Kinetics Of ◽  
Reduced Temperature

D2O and perchlorate manifest opposing effects on the contractile function of skeletal muscle (amplitude of twitches and maximum K contractures, potential dependence of contraction activation and inactivation), and when combined the influence of one may effectively antagonize that of the other. The ratio of perchlorate concentrations required to produce effects of equal intensity (e.g., twitch enhancement and restoration of maximum K contractures in media lacking divalent cations or containing a depressant concentration of a cationic amphipath) in H2O and D2O solutions was generally rather constant. These findings are compatible with the view that both agents can influence contractile function by virtue of their effects on solvent structure. In the absence of divalent cations, the effects of reduced temperature resemble those of D2O whereas the effects of increased temperature resemble those of the chaotropic anion. However, in other media, variation in temperature was found to result in additional nonsolvent effects so that low temperature could oppose rather than enhance the effects of D2O. These observations are discussed in terms of a model which postulates a role for solvent influences on the kinetics of two separate potential-dependent conformational transitions of membrane proteins which mediate the activation and inactivation of contraction in skeletal muscle.

The effects of temperature, local anaesthetics, pH, divalent cations, and group-specific reagents on repriming and repolarization-induced contractures in frog skeletal muscle

1979 ◽  
Vol 57 (6) ◽  
pp. 619-630 ◽  
Author(s):  
J. G. Foulks ◽  
Florence A. Perry
Keyword(s):  
Resting State ◽  
Time Course ◽  
Divalent Cations ◽  
Local Anaesthetics ◽  
Alkaline Ph ◽  
Amino Groups ◽  
Small Reduction ◽  
Effects Of Temperature ◽  
Sufficient Reduction ◽  
Dependent Processes

Contractures appear during repolarization of frog toe muscles in media containing perchlorate in place of chloride. These contractures were suppressed or delayed by certain procedures which retard the repriming of K contractures, i.e., by sufficient reduction in temperature or by alkaline pH in solutions lacking divalent cations. They also were greatly reduced without interference with repriming after treatment with a reagent which selectively modifies free amino groups. In the presence of appropriate concentrations of procaine, repriming was markedly impaired with only a small reduction in the amplitude of repolarization-induced contractures. Small contractures were produced during repolarization in chloride solutions in the presence of 10 mM procaine at pH 8.0. None of these procedures affected the changes produced by perchlorate solutions in the potential dependence and the time course of K contractures. The results support the view that activation and inactivation of contraction following depolarization are separate potential dependent processes. Tension appears to develop during repolarization when the reversal of inactivation occurs before the reversal of activation is completed, both steps being necessary to recover the reprimed resting state.

Increased sensitivity of frog skeletal muscle to procaine in the presence of organic anions

1978 ◽  
Vol 56 (5) ◽  
pp. 739-746 ◽  
Author(s):  
J. G. Foulks ◽  
F. A. Perry
Keyword(s):  
Action Potentials ◽  
Time Course ◽  
Organic Anion ◽  
Organic Anions ◽  
Depressant Effect ◽  
Alkyl Sulfonates ◽  
Carboxylate Anions ◽  
Increased Sensitivity ◽  
Local Anaesthetic Action ◽  
Anaesthetic Action

In solutions containing an organic anion in place of chloride, frog toe muscles displayed increased sensitivity to the local anaesthetic action of procaine. Twitch inhibition by procaine in all media was accompanied by suppression of action potentials without change in membrane resting potentials. The twitch depressant effect of procaine was greater in solutions with carboxylate anions than with alkyl sulfonates. The intensity and the rapidity of onset of the effects of organic anions was related to the size of their hydrophobic component.Procaine accentuated acetate-induced reductions in the [K]0 required to produce K contractures and in the time course of submaximum K contractures. These effects were not shared by benzocaine. They were antagonized by increased [Ca]0.The results indicate that separate agents can exert mutually enhancing actions from opposite surfaces of the sarcolemma to facilitate the inactivation of depolarization-induced excitation–contraction coupling as well as that of the potential-dependent sodium channel.

Biphasic temporal pattern in exercise capacity after myocardial infarction in the rat: relationship to left ventricular remodeling

2005 ◽  
Vol 288 (1) ◽  
pp. H244-H249 ◽  
Author(s):  
Nathan A. Trueblood ◽  
Patrick R. Inscore ◽  
Daniel Brenner ◽  
Daniel Lugassy ◽  
Carl S. Apstein ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Exercise Capacity ◽  
Time Course ◽  
Ventricular Remodeling ◽  
Contractile Function ◽  
Left Ventricular ◽  
Coronary Artery Ligation ◽  
Early Recovery ◽  
Functional Changes ◽  
Lv Remodeling

After myocardial infarction (MI), there is progressive left ventricular (LV) remodeling and impaired exercise capacity. We tested the hypothesis that LV remodeling results in structural and functional changes that determine exercise impairment post-MI. Rats underwent coronary artery ligation ( n = 12) or sham ( n = 11) surgery followed by serial exercise tests and echocardiography for 16 wk post-MI. LV pressure-volume relationships were determined using a blood-perfused Langendorff preparation. Exercise capacity was 60% of shams immediately post-MI ( P < 0.05) followed by a recovery to near normal during weeks 5– 8. Thereafter, there was a progressive decline in exercise capacity to ±40% of shams ( P < 0.01). At both 8 and 16 wk post-MI, fractional shortening (FS) was reduced and end-diastolic diameter (EDD) was increased ( P < 0.01). However, neither FS nor EDD correlated with exercise at 8 or 16 wk ( r2 < 0.12, P > 0.30). LV septal wall thickness was increased at both 8 ( P = 0.17 vs. shams) and 16 wk ( P = 0.035 vs. shams) post-MI and correlated with exercise at both times ( r2 ≥ 0.50 and P ≤ 0.02 at 8 and 16 wk). Neither end-diastolic volume nor maximum LV developed pressure at 16 wk correlated with exercise capacity. Exercise capacity follows a biphasic time course post-MI. An immediate decrease is followed by an early recovery phase that is associated with compensatory LV hypertrophy. Subsequently, there is a progressive decrease in exercise capacity that is independent of further changes in LV volume or contractile function.

scholarly journals Positive Inotropic Effects of ATP Released via the Maxi-Anion Channel in Langendorff-Perfused Mouse Hearts Subjected to Ischemia-Reperfusion

2021 ◽  
Vol 9 ◽  
Author(s):  
Hiroshi Matsuura ◽  
Akiko Kojima ◽  
Yutaka Fukushima ◽  
Yu Xie ◽  
Xinya Mi ◽  
...  
Keyword(s):  
Contractile Function ◽  
Organic Anion ◽  
Left Ventricular ◽  
Transient Increase ◽  
Tyrode Solution ◽  
Inotropic Effects ◽  
Cl Channel ◽  
Short Period ◽  
Cl Channels ◽  
Normal Tyrode Solution

The organic anion transporter SLCO2A1 constitutes an essential core component of the ATP-conductive large-conductance anion (Maxi-Cl) channel. Our previous experiments using Langendorff-perfused mouse hearts showed that the Maxi-Cl channel contributes largely to the release of ATP into the coronary effluent observed during 10-min reperfusion following a short period (6 min) of oxygen-glucose deprivation. The present study examined the effect of endogenous ATP released via Maxi-Cl channels on the left ventricular contractile function of Langendorff-perfused mouse hearts, using a fluid-filled balloon connected to a pressure transducer. After the initial 30-min stabilization period, the heart was then perfused with oxygen-glucose-deprived Tyrode solution for 6 min, which was followed by a 10-min perfusion with oxygenated normal Tyrode solution in the absence and presence of an ATP-hydrolyzing enzyme, apyrase, and/or an adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). In the absence of apyrase and DPCPX, the left ventricular developed pressure (LVDP) decreased from a baseline value of 72.3 ± 7.1 to 57.5 ± 5.5 mmHg (n = 4) at the end of 6-min perfusion with oxygen-glucose-deprived Tyrode solution, which was followed by a transient increase to 108.5 ± 16.5 mmHg during subsequent perfusion with oxygenated normal Tyrode solution. However, in the presence of apyrase and DPCPX, the LVDP decreased to the same degree during 6-min perfusion with oxygen-glucose-deprived Tyrode solution, but failed to exhibit a transient increase during a subsequent perfusion with oxygenated normal Tyrode solution. These results strongly suggest that endogenous ATP released through Maxi-Cl channels contributes to the development of transient positive inotropy observed during reperfusion after short-period hypoxia/ischemia in the heart.

scholarly journals Testosterone modulates cardiomyocyte Ca2+ handling and contractile function

2009 ◽  
pp. 293-297 ◽  
Author(s):  
CL Curl ◽  
LMD Delbridge ◽  
BJ Canny ◽  
IR Wendt
Keyword(s):  
Sex Differences ◽  
Cardiac Function ◽  
Time Course ◽  
Direct Evidence ◽  
Contractile Function ◽  
Testosterone Replacement

The extent to which sex differences in cardiac function may be attributed to the direct myocardial influence of testosterone is unclear. In this study the effects of gonadal testosterone withdrawal (GDX) and replacement (GDX+T) in rats, on cardiomyocyte shortening and intracellular Ca2+ handling was investigated (0.5 Hz, 25 o C). At all extracellular [Ca2+] tested (0.5-2.0 mM), the Ca2+ transient amplitude was significantly reduced (by ~ 50 %) in myocytes of GDX rats two weeks postgonadectomy. The time course of Ca2+ transient decay was significantly prolonged in GDX myocytes (tau, 455±80 ms) compared with intact (279±23 ms) and GDX+T (277±19 ms). Maximum shortening of GDX myocytes was markedly reduced (by more than 60 %) and relaxation significantly delayed (by more than 35 %) compared with intact and GDX+T groups. Thus testosterone replacement completely reversed the cardiomyocyte hypocontractility induced by gonadectomy. These results provide direct evidence for a role of testosterone in regulating functional Ca2+ handling and contractility in the heart.

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